I'm moving to London in two months from the US and was wondering if it was possible to use my iPhone 4S over there. I am currently on AT&T so I know the networks are compatible, but I think I have read somewhere that the lock my phone so I cannot use another companies sim card. What would I need to do to use my phone over there? It would be a lot easier if I did not have to buy a new phone. Any help is greatly appreciated.