I had the same SIM card since 2004. It went into 4 different phones, got swapped in and out of my last phone on a couple vacations in Europe where I used a prepay on a local network for in-country calls. And etc. Basically, no worries. Until the fateful day when the phone just STOPPED sending or receiving calls. I could see bars, lots of bars, but no connection even when trying to manually select T Mo as network. The Tech Support girl suggested new SIM. That cured the problem. I guess sometimes they just go bad.