MY iPhone does not always ring when I am getting inbound calls. The calls will go into my voicemail. The ringer is on and the call forwarding function is not on. It is very strange as I will miss two calls and then a third call will go through and my phone rings. Also, another member of my family plan always has to call two times before her calls to me go through. Is there a way to stop this? I have missed some very important calls over the last few days. I am concerned that I will miss an emergency phone call. This never happened to me when I was on the AT&T network.