i haven't read through this entire thread, but i just wanted to post a temporary fix that works for me...how long it keeps my phone working, im not sure...so i do it every few hours..and i'm not having anymore problems receiving calls (verizon, iphone 5).
go to settings>do not disturb> enable it, then disable it.
i posted this on another related thread, but i figured i'd throw it on here too. emphasis on the word "temporary". everytime my girlfriend would call me, it would ring, and go to voicemail without any notification of a missed call. she would text me saying she tried to call...after messing around a bunch, this is what i finally came up with. i also tested it from my work line. called my phone...iphone doesn't ring, no missed call notification. i enable/disable "do not disturb", then call my phone again from the same work line, the call goes through.
Like i said, it isn't permanent, which is why i just do it every few hours. Hope this helps.