Before I start, I already have the iPhone 4 on AT&T. My girlfriend has t-mobile and I originally bought her an iPhone 4 when it launched and unlocked it using ultrasnow for T-mobile. A few months ago the microphone went out and I had to send it in to apple to fix. When I received the new phone,the baseband was updated and she was no longer able to use it on T-mobile. Being that the new iPhone 4s is considered a world phone does that mean I can purchase the phone for her and it will work on T-mobiles 2g service? She already has a blackberry with a year and change left on her contract but has been more than begging for the white iPhone. Anniversary is this week and getting her the 4s by the 14th would be clutch...... Any ideas as to if this is truly a world phone and will work with any GSM? I don't mind paying the $650 just to get her the phone...... I do know that currently the phone will be locked with whatever carrier you use but my main concern is with T-mobile working. I also have a sim cutter if that's an obstacle.