My wife's is all over the place with this issue.
It will read 4 bars of 4g, and once she makes a call it reads " no sim card". After a few attempts to make a call it will finally connect. But after she hangs up, she gets the same message. Some, text go through, some give her the " no mobile network available".
VZW said its because we used a new sim card, but switched back to the old one and they programmed it, erased the other, and she still has the same issues.
So now, vzw says that all the Sims were bad, and they are sending a new sim. but the sim that came in the box was new as well. Sucks to not have a phone she can't use. Sucks to call her and not know if this is the call that is going to go through, or the call that's going straight to voicemail.
The Vzw rep said that the 4g fall out is a known issue, and would require a reboot. But she hadn't experience anything like this where the phone is selectively disconnecting from the sim card.
And for the record, the sim card has been inserted and reseated 100 times, to include power cycles.
What's left to do? Wait for another sim? Reconnect her rooted Gnex that had a poor signal, but never lost a call.
Kinda frustrated.