I tried to config that when customer press 4, they will auto Dial back to my RingGroup 101
exten => 4,1,Dial(SIP/101)
But I got this problem
[2017-11-13 04:42:31] VERBOSE[3349][C-00000049] pbx.c: Executing [4@trongtest:1] Dial("SIP/Trong_Trunk-00000094", "SIP/101") in new stack
[2017-11-13 04:42:31] WARNING[3349][C-00000049] chan_sip.c: Purely numeric hostname (101), and not a peer--rejecting!
[2017-11-13 04:42:31] WARNING[3349][C-00000049] app_dial.c: Unable to create channel of type 'SIP' (cause 20 - Subscriber absent)
[2017-11-13 04:42:31] VERBOSE[3349][C-00000049] app_dial.c: Everyone is busy/congested at this time (1:0/0/1)
[2017-11-13 04:42:31] VERBOSE[3349][C-00000049] pbx.c: Auto fallthrough, channel 'SIP/Trong_Trunk-00000094' status is 'CHANUNAVAIL'
Please, help me to solve this. Thanks you guys!