Below is a clean, complete PJSIP configuration in one block for your BSNL IMS SIP trunk using: DID: +9179XXXXXXXX Username: +9179XXXXXXXX Password: CEWBYXXXXX IMS Server: 10.191.25.1 Domain: gj.stbi.ims.bsnl.in You can copy-paste directly into pjsip.conf . Complete BSNL PJSIP Configuration ;============================== ; TRANSPORT ;============================== [transport-udp] type=transport protocol=udp bind=0.0.0.0 ;============================== ; AUTHENTICATION ;============================== [BSNL_AUTH] type=auth auth_type=userpass username= +9179XXXXXXXX password=CEWBYXXXXX ;============================== ; AOR ;============================== [BSNL_AOR] type=aor contact=sip:10.191.25.1:5060 qualify_frequency=60 ;============================== ; ENDPOINT ;============================== [BSNL] type=endpoint transport=transport-udp context=from-trunk disallow=all allow=ulaw allow=alaw aors=BSNL_AOR outbound_auth=BSNL_AUTH from_user= +9179XXXXXXXX from_domain=gj.stbi....