My iPhone 5 has a strange problem with voicemail. If someone places a call to me, it will go right into voicemail, when it shouldn't (I'm not on the phone, and my phone is not dead). If they call me right back, the call will go through. I.e., initial calls go into voicemail; a second call from the same number will go through. So if the person knows about the problem and calls me right back, I can get the call. Otherwise, I just get messages. Why would voicemail pick up on a 1st call, and then not pick up on a 2nd call from the same number (provided the 2nd call is made right after the first)? I have it set to pick up after 4 rings. Weird issue.