...T-Mobile Sim Card? I recently lost my T-Mobile cell phone. I had an IPhone 4 from ATT that I plan to use as a replacement. I had gotten the unlock code for the phone a while back but had not officially unlocked the IPhone since it required a sim card. I went to T-Mobile and asked for a SIM card for the phone. They gave me one, I inserted the sim card and it did not register it when I tried to get it restored. I then restored the IPhone by itself and wiped it completely. The IPhone will not register the T-Mobile sim card and will not go to the main menu. Do I need an ATT Sim Card to re-activate the Phone?