Hi all, I bought last week an ATT off-contract iPhone 5 to be used overseas in a few weeks. I started to use my phone with my current ATT account and checked it with a Tmobile sim to make sure it is unlocked. However, a friend of mine says that the phone he bought last year from the Apple store was unlocked and worked fine with Tmobile in the US; BUT it would not work overseas after he left the US. He claims if the phone is activated/used (the first use) in the US, it is somehow locked to the US carriers. Can something like this be true? I am now a little bit worried. He said he had to return the phone to Apple ultimately. Thank you for your comments.