During its Q & A, T-Mobile's just confirmed that if your purchase one of its phones under its new contract / non-contract "UnCarrier" system, you'll be obligated to buy it out -- but you could keep making monthly payments, or even trade it for another device. If you opt for the latter, you'll get "fair market credit," for your handset, according to the carrier, which said it would decide such a value. In other news, all phones sold will be locked -- so should you decide to switch and keep the phone, you're gonna need T-Mo's help.