I have SIP trunk from SIP provider, I configured the VG to run CUBE I can place calls to PSTN. but if some body called from PSTN to IP phone and the user answers the call the calling party still hear the ringing tone while the IP phone shows connected and counters count the seconds of the call.
there is another strange issue. after 10 seconds from answering the calls another call reach to the IP phone from the same calling number in other words you will see on the phone like this:
1 from 1237654 connected 13 s
2 from 1237654 (ringing)
after answering the second calls the call will disconnect ( but for the calling party still the call not answered at the end he receive call no answer)
I contacted the SIP provider and they inform me that they can not see any other invite message forwarded to my line.