My system is: 3CX v8 Snom 870 Spa3102 voip (CallCentric) pstn When I call thru the pstn line IVR DTMF works fine. When I call via the voip line, some time the receiving IVR system may not recognize the DTMF tones. I usually at that point dial out on the pstn line to make it work. Because I am using the same phone (snom) for both calls, I would assume that it is an issue with the 3CX system. Any thoughts?