Seeing as I am going to be out in the US over the launch week, I was wondering if it was possible to purchase a PAYG (no commitment) iPhone 4 in the US, and then pop my O2 SIM in when I get back to the UK? I see that various store in the US have said they will be sellig the iPhone 4 on launch (Walmart, Best Buy etc), and I wondered if these (the no commitment/PAYG versions) would be locked to AT&T or do they lock to the first SIM that you put in? If it's the latter, if I don't even switch the phone on until I get back to the UK, and the first thing I do is put my UK O2 SIM in it, would that work? Or is this idea really a non starter? Thanks.