I am considering purchasing an unlocked Xperia ZR and i have At&t network. Can i udate the software once i put my at&t sim card in this ZR because the phone will come with 4.1 installed but i have read it is elligible for an update to 4.2. My question is, since it isnt technically an at&t phone but rather an unlocked phone i just put my sim in, will it still update? I dont know much about this kind of thing.