Hello, I am appreciate if there is any one who can help me. Recently I was testing our 3CX system and found out that when we call external number wineshark will see a 180 ringtone to original caller the phone will start to ring. If the external number is busying calling the phone will not hear a ringback announcement. The phone will keep ringing. I build up a same system same hyper-v, subnet then only add SIP trunk than test with one of our ip phone. Winshark will see a 183 secession if the number is busy than the original caller will hear a announcement a few second. Could somebody tell if there are any setting could change?