Hi! Lately my friend has been having trouble calling me, his call can't get through and my phone won't tell me someone is calling, but as soon as he hangs up, I get a message saying I have a missed call. I didn't block his number, I even tried deleting his contact and adding him again, which resulted in one successful call from him until it started doing it again. No other people in my contact list have this problem. Is there something in the phone I can do or is this more likely a provider issue? Thanks!