I finally set up the call forward all on line C (the last line on the hunt group) using *72 to a VoIP line. It works in a way that when i call line C, it rings on the VoIP line successfully. But when i call make line A and B busy, and make third call to line A, I expected the voip line to ring. But the VoIP line doesn't ring, it gives me busy signal to the caller. :( problem unsolved.
Roger
