Audio transfers back to phone

Hey guys,
I am having the problem with chan_mobile… I could successfully connect, pair and dial the mobile device using bluetooth dongle with asterisk but when after I connect, when the calls goes out, mobile phone keeps the audio on phone instead of transferring to bluetooth device…This doesnot happen everytime but, 3 out of 5 attempts are not forwarded to bluetooth…
My hciconfig report:
Type: BR/EDR Bus: USB
BD Address: 00:11:67:AD:3F:12 ACL MTU: 1021:8 SCO MTU: 48:10
UP RUNNING PSCAN ISCAN
RX bytes:4716008 acl:925 sco:90914 events:2324 errors:0
TX bytes:20770 acl:811 sco:0 commands:564 errors:0
Features: 0xff 0xfe 0x8d 0x3e 0x88 0x19 0x00 0x00
Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3
Link policy: RSWITCH HOLD SNIFF
Link mode: SLAVE ACCEPT
Name: 'ubuntu-2’
Class: 0x580100
Service Classes: Capturing, Object Transfer, Telephony
Device Class: Computer, Uncategorized
HCI Version: 2.0 (0x3) Revision: 0x2c6
LMP Version: 2.0 (0x3) Subversion: 0x2c6
Manufacturer: Integrated System Solution Corp. (57)
My asterisk version is : 10.1.3
my phone is nokia d5130

please help me…!!