You need not change your contract. You can continue using the same T-mobile network. Once when your contract is over in 2 months, you can get an upgrade to iPhone. If T-mobile doesn't provide you an iPhone, you can get a cheap network locked iPhone from online, unlock and use it with your T-mobile network. To unlock an iPhone, you can visit SimpleUnlocking.com and get the remote unlocking service. This method of unlocking an iPhone is safe, simple, affordable, quick and permanent. It doesn't require a jailbreak too. Good luck.