I just checked my cell phone to see if I missed and calls and my external screen read, "No Service". So naturally I'm confused because I've never seen that message before, and I open up my phone and where it normally reads, "Cingular" it read "Unregistered SIM". What does this mean? I paid my bills on time, I didn't go over my minutes. Anyone have an idea? I have a Motorola V600 through Cingular if it helps at all.