I purchased my iPhone in the U.S. and moved to Singapore. The phone was obviously locked to AT&T and did not work on Singapore carriers. However, I requested a new phone through the warranty program and the iPhone they returned to me was unlocked. It is illegal in Singapore to sell a carrier locked phone. After several months of use on StarHub, it required a restore in which it relocked it to AT&T. Applecare explained to me that when it was restored, the serial number was matched to my AT&T profile. I again requested a new phone through the warranty program and again they returned to me an unlocked phone. Will the SAM IMEI unlock backup work in my case? I'm afraid if I deactivate and activate, it will lock it once again to AT&T.