[gsmsubscriber]
exten=>_XXXXXXXXXX,1,Dial(PJSIP/GSM/sip:${EXTEN}@192.168.75.144:5069)
exten=>_XXXXXXXXXX,n,Playback(vm-nobodyavail)
exten=>_XXXXXXXXXX,n,HangUp()

exten=>s-CHANUNAVAIL,1,Playtones(unobtainable)
exten=>s-CHANUNAVAIL,n,wait(10)
exten=>s-CHANUNAVAIL,n,HangUp()

exten=>s-BUSY,1,Playtones(busy)

exten=>_911,1,Dial(PJSIP/GSM/sip:1234567892@192.168.75.144:5069)