Not sure if this is the right forum, but I will try: My home button on my iPhone 4 stopped working recently after I moved to China. I went to a local service center and, since the phone was still under Applecare, they replaced it with a new one. The iPhone was bought in the US and locked to AT&T. The repair guy said that the new one would be locked as well but that there might be a grace period in which I can use it with a non-AT&T SIM. I just tried with a local SIM card and it works fine but I'm now wondering if it will stop working all of a sudden. I have never heard of a grace period and wanted to check if anyone here had. Also, I have yet to hook it up with iTunes since I'm wondering if that might lock the phone as well. Any thoughts? Thanks!