So, I was shopping around for iPhone 4s' and came to realize I have to buy it factory unlocked to use it on T-Mobile, (My network carrier duh. lol) Anyway, it costs like, $549.00 or something like that. I don't want to pay that much. So I was wondering if there was a way for me to get an iPhone 4s on any carrier and somehow use it on T-Mobile...? Is there an app that I can download or do I HAVE to buy it factory unlocked...? Oh and also, should I get it black or white? Please and thanks. !!