FYI
In the last few years, I had few factory unlocked, YOU DON'T NEED TO BACKUP/RESTORE YOUR IPHONE, JUST REMOVE YOUR AT&T SIM CARD AND INSERT A NEW ONE (T-MOBILE/SIMPLEMOBILE ETC), then connect to iTunes and wait for the activation, you will fet this message "Congratulations your iPhone has been unlocked"
Sometimes you don't get it, even with NIB factory unlocked (running 5.0).
In the last few years, I had few factory unlocked, YOU DON'T NEED TO BACKUP/RESTORE YOUR IPHONE, JUST REMOVE YOUR AT&T SIM CARD AND INSERT A NEW ONE (T-MOBILE/SIMPLEMOBILE ETC), then connect to iTunes and wait for the activation, you will fet this message "Congratulations your iPhone has been unlocked"
Sometimes you don't get it, even with NIB factory unlocked (running 5.0).