How register users from openbts in asterisk

look, this is my error to the moment to realize a call

== Using SIP RTP CoS mark 5 -- Executing [1000@sip-external:1] Dial("SIP/IMSI730030700128232-00000001", "SIP/IMSI730011855337041") in new stack == Using SIP RTP CoS mark 5 [Apr 8 18:57:03] WARNING[5215]: app_dial.c:1780 dial_exec_full: Unable to create channel of type 'SIP' (cause 20 - Unknown) == Everyone is busy/congested at this time (1:0/0/1) -- Auto fallthrough, channel 'SIP/IMSI730030700128232-00000001' status is 'CHANUNAVAIL'
sip show registry: Host dnsmgr Username Refresh State Reg.Time 0 SIP registrations.
sip show peers

Name/username              Host            Dyn Nat ACL Port     Status     
IMSI7300xxxxxxxxxx        (Unspecified)    D   N      5060     Unmonitored 
IMSI7300xxxxxxxxxx        (Unspecified)    D   N      5060     Unmonitored 
IMSI7300xxxxxxxxxx        (Unspecified)    D   N      5060     Unmonitored 
3 sip peers [Monitored: 0 online, 0 offline Unmonitored: 3 online, 0 offline][/code]

sip.conf
[code][IMSI7300xxxxxxxxxxx]
;Yo javier ricke
type= friend
callerid= <1000>
canreinvite= yes
context= sip-external
allow= gsm
host= dynamic
dtmfmode= info
allowguest=yes
insecure=port 

[IMSI7300xxxxxxxxxxx]
type= friend
;Samsung gt-s5360l
callerid= <1001>
canreinvite= yes
context= sip-external
allow= gsm
host= dynamic
dtmfmode= info
allowguest=yes
insecure=port 

[IMSI7300xxxxxxxxxxx]
;Sony Ericsson Xperia
type= friend
callerid= <1002>
canreinvite= yes
context= sip-external
allow= gsm
host= dynamic
dtmfmode= info
allowguest=yes
insecure=port [/code]

extensions.conf

[code][sip-external]
; local extensions

exten => 1000,1,Dial(SIP/IMSI730xxxxxxxxxxxx)
exten => 1001,1,Dial(SIP/IMSI730xxxxxxxxxxxx)
exten => 1002,1,Dial(SIP/IMSI730xxxxxxxxxxxx)

i dont understand what happen, in all manual of openbts appear host=dynamic and work!
i dont know why to a me dont working!

regards