My cousin passed down to my dad this phone and he's already using a T-mobile SIM on his other phone. Apparently this HTC is locked only for Verizon and he wants to unlock it for T-Mobile but those cell phone store guys tell him that the phone has to be "brand new" in order for them to unlock it for him. Is this really how it works? I've done a lot of research on Google but nothing helps, so I'm hoping you guys would know! He's already planning to sell it, but it's still in flawless condition!