I have this problem. My phone is included on RingGroup1. I make or recive a call, then when i'm speaking, 3CX recive a call and send this call to RingGroup1. Now i end my call (when RingGroup1 is ringing) and i suppose that my phone must ring (because my phone is in RingGroup1), but my phone remain silence. I use the last version of 3cx (not V.6) and LinkSys SPA 922.