You simply order an unlock key . Mine was around $24 from
HTC SIM Unlock codes HTC Remote Unlock HTC Unlocking HTC SIM-Unlock | Unlock-Now.com then you just put your sim card from a carrier other than what the phone is (your t-mobile sim) on the sprint phone . It will ask you to enter the unlock code and thats it . just enter the number sent to you and will now be unlocked .