Rajal,
Please post your configuration as this will give those trying to help and idea of what you have and aid in trying to assist you.
With that said, connect to the asterisk to see what its doing "asterisk -r" look to see if you get something like this;
er 'sendcron' logged on from 127.0.0.1
[May 29 10:13:09] == Spawn extension (default, 58600055, 1) exited non-zero on 'Local/58600055@default-2f2c,2'
[May 29 10:13:09] -- Executing [h@default:1] DeadAGI("Local/58600055@default-2f2c,2", "agi://127.0.0.1:4577/call_log--HVcauses--PRI-----NODEBUG-----0---------------") in new stack
[May 29 10:13:09] -- AGI Script
agi://127.0.0.1:4577/call_log--HVcauses ... ---------- completed, returning 0
[May 29 10:13:09] == Spawn extension (default, 8309, 3) exited non-zero on 'Local/58600055@default-2f2c,1'
[May 29 10:13:09] -- Executing [h@default:1] DeadAGI("Local/58600055@default-2f2c,1", "agi://127.0.0.1:4577/call_log--HVcauses--PRI-----NODEBUG-----0---------------") in new stack
[May 29 10:13:09] -- AGI Script
agi://127.0.0.1:4577/call_log--HVcauses ... ---------- completed, returning 0
[May 29 10:13:10] -- Accepting AUTHENTICATED call from 192.168.40.27:
if you will notice the 'dead agi' if every call made is showing that then your problem is with your SIP trunks, either a NAT issue or something similar. Also check the caller ID that your sending, some SIP provider or their carriers dont like blank ID's or all 0's