Steve unlocked his T-Mobile phone when he went overseas, but when he came back to the US, T-Mobile locked it back down again. Leo said to ask T-Mobile to unlock it again, and they gave him a new unlock code. He can't get to the point where he can enter the code, though. Leo says he can try dialing the code in the dialer as if he's calling it, and that might unlock it.
Leo says when he gets his next phone, he should just buy it unlocked. It won't be subsidized, but then he can put other SIM cards in it and it will never be locked.