UPDATE: the problem happened again last night and I brought my GN to the Verizon store this morning. They replaced the SIM card. I then left and a couple of hours later I couldn't make or receive calls. Even the My Verizon app couldn't log me in because it wouldn't recognize my number. I went back to the Verizon store and they took my phone, pulled the battery and SIM card, waited a few minutes and then put them back. Miraculously everything was fine and I could make and receive calls again. I did have to re-register with My Verizon as my account all of sudden became inactive. As usual, the Verizon people have no idea why all this happened and tried to sales talk me into signing up for a new phone. SMH.