I just unlocked my iPhone via iPhone SimFree software. The thing is that I know the iPhone is unlocked since when I put a non AT&T SIM it won't complain or tell me invalid SIM, it just goes ahead and retreives the voicemails and adopts the new number; however, the iPhone won't pick up the signal of the new carrier. It stays at 1 bar and I can not make or receive a call. What do I need to do next? PS - I am using Windows XP.