[gsm]
exten => _X.,1,Set(MAX=16)
exten => _X.,2,Dial(VGSM/mobilink-${MAX}/0${EXTEN:2})
exten => _X.,n,Noop(${DIALSTATUS})
exten => _X.,n,GotoIf($[ "${DIALSTATUS}" : "CHANUNAVAIL" ]?${EXTEN},$[ ${PRIORITY} + 2 ]:${EXTEN},$[ ${PRIORITY} + 1 ])
exten => _X.,n,GotoIf($[ "${DIALSTATUS}" : "CONGESTION" ]?${EXTEN},$[ ${PRIORITY} + 1 ]:stophere,1)
exten => _X.,n,SetVar(MAX=$[ ${MAX} - 1 ])
exten => _X.,n,GotoIf(${MAX}?${EXTEN},2:stophere,1)
exten => stophere,1,Congestion()