I just bought an AT&T Galaxy S5 brand new, and got AT&T to unlock it for me so I could use it on T-mobile. Now that it's unlocked, what will happen if I factory reset the phone? Will it re-lock? If so, will the code they gave me still work to unlock it again? I may want to factory reset it at some point, but I'm afraid it will lock again. Going through the unlock process with AT&T was not fun.