I had a strange one last night. I called my wife (using my iPhone 4S, she uses the 5). The phone rang off the hook, so I left a message. When I returned home, she said the phone was right next to her and it never rang. When I checked there was no missed call indicator and the voice mail I left was not there. I decided to check it out. I called her phone again, staring at it, and sure enough, no ring on her phone. I then tried my daughter (iPhone 4) and it rang just fine. We tried my wife's phone again, and this time it rang, and about 30 seconds later the voice message appeared (from the previous call).
Kinda, strange. Does this sound like an iPhone problem, or a "tower" problem. At all times the iPhone 5 reported a strong cell signal.