Audio problem with Public Network

Hi I am newbie here.

I have just installed and configured Asterisk 17 in a desktop PC running Ubuntu 18.4
My Asterisk and one of the clients using Zoiper Softphone are behind NAT. Another Client is an iPhone running on 4G network. I have configured my router to forward 5060/UDP and ports 10000-20000/UDP as well.
Problem I am having is when one client calls the other, the call goes through, but no audio is present in either client.

However, when I put both clients behind the NAT use local ip i.e. 192.168.0.2 in both clients as host then everything is perfect.

Here is my pjsip.conf file

[udp-nat]
type=transport
protocol=udp
bind=0.0.0.0
local_net=192.168.0.0/24 (My LAN Network)
;local_net=127.0.0.1/24
external_media_address=112.xx.xx.0 (My WAN IP Address)
external_signaling_address=112.xx.xx.0


[6001]
type = endpoint
transport=udp-nat
context=users
disallow=all
allow=ulaw
aors=6001
auth=6001
direct_media=no

[6001]
type=aor
max_contacts=3

[6001]
type=auth
auth_type=userpass
password=*****
username=user1


[6002]
type = endpoint
transport=udp-nat
context=users
disallow=all
allow=ulaw
aors=6002
auth=auth6002
direct_media=no

[6002]
type=aor
max_contacts=1

[auth6002]
type=auth
auth_type=userpass
password=*******
username=user2

Here is the full log after the call goes through:

[Oct  9 16:47:41] DEBUG[12098] res_pjsip_session.c: Applying negotiated SDP media stream 'audio' using audio SDP handler
[Oct  9 16:47:41] DEBUG[12098] res_rtp_asterisk.c: Ignoring duplicate RTCP property on RTP instance '0x7f4da807ecb0'
[Oct  9 16:47:41] DEBUG[12098] res_rtp_asterisk.c: Setting RTCP address on RTP instance '0x7f4da807ecb0'
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Setting tx payload type 0 based on m type on 0x7f4e04ce6df0
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Setting tx payload type 3 based on m type on 0x7f4e04ce6df0
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Copying tx payload mapping 0 (0x5602af20f5c8) from 0x7f4e04ce6df0 to 0x7f4da807ee88
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Copying tx payload mapping 3 (0x5602af20f618) from 0x7f4e04ce6df0 to 0x7f4da807ee88
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Copying tx payload mapping 101 (0x7f4da803f928) from 0x7f4e04ce6df0 to 0x7f4da807ee88
[Oct  9 16:47:41] DEBUG[12098] channel.c: Channel PJSIP/6002-00000003 setting read format path: ulaw -> ulaw
[Oct  9 16:47:41] DEBUG[12098] channel.c: Channel PJSIP/6002-00000003 setting write format path: ulaw -> ulaw
[Oct  9 16:47:41] DEBUG[12098] res_pjsip_session.c: Applied negotiated SDP media stream 'audio' using audio SDP handler
[Oct  9 16:47:41] DEBUG[12098] res_pjsip/pjsip_resolver.c: Performing SIP DNS resolution of target '192.168.0.7'
[Oct  9 16:47:41] DEBUG[12098] res_pjsip/pjsip_resolver.c: Transport type for target '192.168.0.7' is 'UDP transport'
[Oct  9 16:47:41] DEBUG[12098] res_pjsip/pjsip_resolver.c: Target '192.168.0.7' is an IP address, skipping resolution
[Oct  9 16:47:41] DEBUG[12194][C-00000002] channel.c: Channel PJSIP/6002-00000003 setting read format path: ulaw -> ulaw
[Oct  9 16:47:41] DEBUG[12194][C-00000002] channel.c: Channel PJSIP/6001-00000002 setting write format path: ulaw -> ulaw
[Oct  9 16:47:41] DEBUG[12194][C-00000002] channel.c: Channel PJSIP/6001-00000002 setting read format path: ulaw -> ulaw
[Oct  9 16:47:41] DEBUG[12194][C-00000002] channel.c: Channel PJSIP/6002-00000003 setting write format path: ulaw -> ulaw
[Oct  9 16:47:41] DEBUG[12098] res_pjsip_session.c: Applying negotiated SDP media stream 'audio' using audio SDP handler
[Oct  9 16:47:41] DEBUG[12098] res_rtp_asterisk.c: Ignoring duplicate RTCP property on RTP instance '0x7f4da80323d0'
[Oct  9 16:47:41] DEBUG[12098] res_rtp_asterisk.c: Setting RTCP address on RTP instance '0x7f4da80323d0'
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Setting tx payload type 3 based on m type on 0x7f4e04ce6fc0
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Setting tx payload type 8 based on m type on 0x7f4e04ce6fc0
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Setting tx payload type 0 based on m type on 0x7f4e04ce6fc0
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Copying tx payload mapping 0 (0x5602af20f5c8) from 0x7f4e04ce6fc0 to 0x7f4da80325a8
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Copying tx payload mapping 3 (0x5602af20f618) from 0x7f4e04ce6fc0 to 0x7f4da80325a8
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Copying tx payload mapping 8 (0x5602af20f7a8) from 0x7f4e04ce6fc0 to 0x7f4da80325a8
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Copying tx payload mapping 97 (0x7f4da8099d78) from 0x7f4e04ce6fc0 to 0x7f4da80325a8
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Copying tx payload mapping 101 (0x7f4da807eab8) from 0x7f4e04ce6fc0 to 0x7f4da80325a8
[Oct  9 16:47:41] DEBUG[12098] rtp_engine.c: Copying tx payload mapping 110 (0x7f4da80952e8) from 0x7f4e04ce6fc0 to 0x7f4da80325a8
[Oct  9 16:47:41] DEBUG[12098] channel.c: Channel PJSIP/6001-00000002 setting read format path: ulaw -> ulaw
[Oct  9 16:47:41] DEBUG[12098] channel.c: Channel PJSIP/6001-00000002 setting write format path: ulaw -> ulaw
[Oct  9 16:47:41] DEBUG[12098] res_pjsip_session.c: Applied negotiated SDP media stream 'audio' using audio SDP handler
[Oct  9 16:47:41] DEBUG[12194][C-00000002] stasis.c: Creating topic. name: bridge:all/bridge:79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a, detail: 
[Oct  9 16:47:41] DEBUG[12194][C-00000002] stasis.c: Topic 'bridge:all/bridge:79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a': 0x7f4de00055f0 created
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a' can not use native RTP bridge as two channels are required
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge technology native_rtp is not compatible with properties of existing bridge.
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge technology holding_bridge does not have any capabilities we want.
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge technology softmix has less preference than simple_bridge (10 <= 50). Skipping.
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Chose bridge technology simple_bridge
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: calling simple_bridge technology constructor
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: calling simple_bridge technology start
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge_channel.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: 0x7f4de000aec0(PJSIP/6002-00000003) is joining
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge_channel.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: pushing 0x7f4de000aec0(PJSIP/6002-00000003)
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a' can not use native RTP bridge as two channels are required
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge.c: Bridge technology native_rtp is not compatible with properties of existing bridge.
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge.c: Bridge technology holding_bridge does not have any capabilities we want.
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge.c: Bridge technology softmix does not have any capabilities we want.
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge.c: Chose bridge technology simple_bridge
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a is already using the new technology.
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: 0x7f4de000aec0(PJSIP/6002-00000003) is joining simple_bridge technology
[Oct  9 16:47:41] DEBUG[12196][C-00000002] channel.c: Dropping duplicate answer!
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge_channel.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: 0x7f4de000b060(PJSIP/6001-00000002) is joining
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge_channel.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: pushing 0x7f4de000b060(PJSIP/6001-00000002)
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Checking compatability for channels 'PJSIP/6002-00000003' and 'PJSIP/6001-00000002'
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge technology simple_bridge has less preference than native_rtp (50 <= 90). Skipping.
[Oct  9 16:47:41] DEBUG[12094] cdr.c: Finalized CDR for PJSIP/6002-00000003 - start 1602240454.676625 answer 1602240461.645606 end 1602240461.648141 dur 6.971 bill 0.002 dispo ANSWERED
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge technology holding_bridge does not have any capabilities we want.
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge technology softmix does not have any capabilities we want.
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Chose bridge technology native_rtp
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: calling native_rtp technology constructor
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: moving 0x7f4de000aec0(PJSIP/6002-00000003) to dummy bridge temporarily
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: 0x7f4de000aec0(PJSIP/6002-00000003) is leaving simple_bridge technology (dummy)
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: calling simple_bridge technology stop
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: 0x7f4de000b060(PJSIP/6001-00000002) is joining native_rtp technology
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Channel 'PJSIP/6001-00000002' is joining bridge tech
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Attaching hook data 0x7f4de000d040 to 'PJSIP/6001-00000002'
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: 0x7f4de000aec0(PJSIP/6002-00000003) is joining native_rtp technology
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Channel 'PJSIP/6002-00000003' is joining bridge tech
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Attaching hook data 0x7f4de0009d30 to 'PJSIP/6002-00000003'
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Tech starting 'PJSIP/6001-00000002' and 'PJSIP/6002-00000003' with target 'none'
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: calling native_rtp technology start
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: calling simple_bridge technology destructor
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Checking compatability for channels 'PJSIP/6001-00000002' and 'PJSIP/6002-00000003'
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge technology simple_bridge has less preference than native_rtp (50 <= 90). Skipping.
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge technology holding_bridge does not have any capabilities we want.
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge technology softmix does not have any capabilities we want.
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Chose bridge technology native_rtp
[Oct  9 16:47:41] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a is already using the new technology.
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Checking compatability for channels 'PJSIP/6001-00000002' and 'PJSIP/6002-00000003'
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge.c: Bridge technology simple_bridge has less preference than native_rtp (50 <= 90). Skipping.
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge.c: Bridge technology holding_bridge does not have any capabilities we want.
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge.c: Bridge technology softmix does not have any capabilities we want.
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge.c: Chose bridge technology native_rtp
[Oct  9 16:47:41] DEBUG[12196][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a is already using the new technology.
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge_channel.c: Setting 0x7f4de000b060(PJSIP/6001-00000002) state from:0 to:1
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge_channel.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: pulling 0x7f4de000b060(PJSIP/6001-00000002)
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge_channel.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: 0x7f4de000b060(PJSIP/6001-00000002) is leaving native_rtp technology
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Channel 'PJSIP/6001-00000002' is leaving bridge tech
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Detaching hook data 0x7f4de0008928 from 'PJSIP/6001-00000002'
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Tech stopping 'PJSIP/6001-00000002' and 'PJSIP/6002-00000003' with target 'none'
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge_native_rtp.c: Discontinued RTP bridging of 'PJSIP/6001-00000002' and 'PJSIP/6002-00000003' - media will flow through Asterisk core
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge_native_rtp.c: Destroying channel tech_pvt data 0x7f4de000d040
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: dissolving bridge with cause 16(Normal Clearing)
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge_channel.c: Setting 0x7f4de000aec0(PJSIP/6002-00000003) state from:0 to:2
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: queueing action type:13 sub:1001
[Oct  9 16:47:45] DEBUG[12094] cdr.c: Finalized CDR for PJSIP/6001-00000002 - start 1602240454.675773 answer 1602240461.646556 end 1602240465.644733 dur 10.968 bill 3.998 dispo ANSWERED
[Oct  9 16:47:45] DEBUG[12194][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a is dissolved, not performing smart bridge operation.
[Oct  9 16:47:45] DEBUG[12196][C-00000002] bridge_channel.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: pulling 0x7f4de000aec0(PJSIP/6002-00000003)
[Oct  9 16:47:45] DEBUG[12196][C-00000002] bridge_channel.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: 0x7f4de000aec0(PJSIP/6002-00000003) is leaving native_rtp technology
[Oct  9 16:47:45] DEBUG[12196][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Channel 'PJSIP/6002-00000003' is leaving bridge tech
[Oct  9 16:47:45] DEBUG[12196][C-00000002] bridge_native_rtp.c: Bridge '79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a'.  Detaching hook data 0x7f4de0009668 from 'PJSIP/6002-00000003'
[Oct  9 16:47:45] DEBUG[12196][C-00000002] bridge_native_rtp.c: Destroying channel tech_pvt data 0x7f4de0009d30
[Oct  9 16:47:45] DEBUG[12196][C-00000002] bridge_channel.c: Channel PJSIP/6002-00000003 will survive this bridge; clearing outgoing (dialed) flag
[Oct  9 16:47:45] DEBUG[12194][C-00000002] app_dial.c: Exiting with DIALSTATUS=ANSWER.
[Oct  9 16:47:45] DEBUG[12194][C-00000002] pbx.c: Spawn extension (users,6002,1) exited non-zero on 'PJSIP/6001-00000002'
[Oct  9 16:47:45] DEBUG[12194][C-00000002] channel.c: Soft-Hanging (0x10) up channel 'PJSIP/6001-00000002'
[Oct  9 16:47:45] DEBUG[12196][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a is dissolved, not performing smart bridge operation.
[Oct  9 16:47:45] DEBUG[12194][C-00000002] channel.c: Channel 0x7f4da802dbb0 'PJSIP/6001-00000002' hanging up.  Refs: 2
[Oct  9 16:47:45] DEBUG[12194][C-00000002] chan_pjsip.c: AST hangup cause 16 (no match found in PJSIP)
[Oct  9 16:47:45] DEBUG[12196][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: actually destroying basic bridge, nobody wants it anymore
[Oct  9 16:47:45] DEBUG[12196][C-00000002] stasis.c: Destroying topic. name: bridge:all/bridge:79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a, detail: 
[Oct  9 16:47:45] DEBUG[12196][C-00000002] stasis.c: Topic 'bridge:all/bridge:79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a': 0x7f4de00055f0 destroyed
[Oct  9 16:47:45] DEBUG[12196][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: calling basic bridge destructor
[Oct  9 16:47:45] DEBUG[12196][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: calling native_rtp technology stop
[Oct  9 16:47:45] DEBUG[12196][C-00000002] bridge.c: Bridge 79f3d59c-1fc1-4e5b-a3f4-9fdcc3dfa03a: calling native_rtp technology destructor
[Oct  9 16:47:45] DEBUG[12196][C-00000002] channel.c: Channel 0x7f4de0003090 'PJSIP/6002-00000003' hanging up.  Refs: 2
[Oct  9 16:47:45] DEBUG[12098] rtp_engine.c: Destroyed RTP instance '0x7f4da80323d0'
[Oct  9 16:47:45] DEBUG[12196][C-00000002] chan_pjsip.c: AST hangup cause 16 (no match found in PJSIP)
[Oct  9 16:47:45] DEBUG[12098] channel.c: Channel 0x7f4da802dbb0 'PJSIP/6001-00000002' destroying
[Oct  9 16:47:45] DEBUG[12188] rtp_engine.c: Destroyed RTP instance '0x7f4da807ecb0'
[Oct  9 16:47:45] DEBUG[12094] stasis.c: Creating topic. name: channel:1602240465.5, detail: 
[Oct  9 16:47:45] DEBUG[12094] stasis.c: Topic 'channel:1602240465.5': 0x7f4dac0029c0 created
[Oct  9 16:47:45] DEBUG[12098] stasis.c: Destroying topic. name: channel:1602240454.3, detail: 
[Oct  9 16:47:45] DEBUG[12098] stasis.c: Topic 'channel:1602240454.3': 0x7f4da8032ba0 destroyed
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(clid) result is '"" <6001>'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE("" <6001>) result is '""""" <6001>"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(src) result is '6001'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(6001) result is '"6001"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(dst) result is '6002'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(6002) result is '"6002"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(dcontext) result is 'users'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(users) result is '"users"'
[Oct  9 16:47:45] DEBUG[12188] res_pjsip/pjsip_resolver.c: Performing SIP DNS resolution of target '192.168.0.7'
[Oct  9 16:47:45] DEBUG[12188] res_pjsip/pjsip_resolver.c: Transport type for target '192.168.0.7' is 'UDP transport'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(channel) result is 'PJSIP/6001-00000002'
[Oct  9 16:47:45] DEBUG[12188] res_pjsip/pjsip_resolver.c: Target '192.168.0.7' is an IP address, skipping resolution
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(PJSIP/6001-00000002) result is '"PJSIP/6001-00000002"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(dstchannel) result is 'PJSIP/6002-00000003'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(PJSIP/6002-00000003) result is '"PJSIP/6002-00000003"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(lastapp) result is 'Dial'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(Dial) result is '"Dial"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(lastdata) result is 'PJSIP/6002,20'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(PJSIP/6002,20) result is '"PJSIP/6002,20"'
[Oct  9 16:47:45] DEBUG[12188] channel.c: Channel 0x7f4de0003090 'PJSIP/6002-00000003' destroying
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(start) result is '2020-10-09 16:47:34'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(2020-10-09 16:47:34) result is '"2020-10-09 16:47:34"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(answer) result is '2020-10-09 16:47:41'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(2020-10-09 16:47:41) result is '"2020-10-09 16:47:41"'
[Oct  9 16:47:45] DEBUG[12188] stasis.c: Destroying topic. name: channel:1602240454.4, detail: 
[Oct  9 16:47:45] DEBUG[12188] stasis.c: Topic 'channel:1602240454.4': 0x7f4de0005310 destroyed
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(end) result is '2020-10-09 16:47:45'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(2020-10-09 16:47:45) result is '"2020-10-09 16:47:45"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(duration) result is '10'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(10) result is '"10"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(billsec) result is '3'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(3) result is '"3"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(disposition) result is 'ANSWERED'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(ANSWERED) result is '"ANSWERED"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(amaflags) result is 'DOCUMENTATION'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(DOCUMENTATION) result is '"DOCUMENTATION"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(accountcode) result is ''
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE() result is '""'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(uniqueid) result is '1602240454.3'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE(1602240454.3) result is '"1602240454.3"'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(userfield) result is ''
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CSV_QUOTE() result is '""'
[Oct  9 16:47:45] DEBUG[12094] pbx_variables.c: Function CDR(sequence) result is '2'
[Oct  9 16:47:45] DEBUG[12094] stasis.c: Destroying topic. name: channel:1602240465.5, detail: 
[Oct  9 16:47:45] DEBUG[12094] stasis.c: Topic 'channel:1602240465.5': 0x7f4dac0029c0 destroyed
[Oct  9 16:47:45] DEBUG[12094] cdr.c: CDR for PJSIP/6002-00000003 is dialed and has no Party B; discarding
[Oct  9 16:47:45] DEBUG[12098] res_pjsip_session.c: BYE received final response code 200```


In my Zoiper softphone app, The Network Settings are as follows:
Transports = UDP
NAT Settings
    rport: Singalling
    Enable STUN = ON
    Server stun.zoiper.com
    Port 3478
    Refresh 30
   
I don't know what is wrong here. Is it a NAT Issue or something else? Please help.