So I just exchanged my USA AT&T-locked iPhone 4 at a UK Apple store for a few hardware issues (unrelated to antennagate), but I can't activate the new phone because it says the sim is unsupported! Now bear in mind Apple said it would work fine and just "needed to be left connected to iTunes for about half an hour" but it's obviously not working an hour later. My sim worked perfectly before transferring to the new handset. I'm panicked, as now I have no phone here. Applecare said I need to contact AT&T, but I know they're going to be useless! Please advise!