G2 by tmobile, i owe the early termination fee, but its not past due, can someone still use it?

Does anyone know if I were to sell it would someone be able to stick their SIM card in it if they already have tmobile and use it? I just don't want to sell a phone with a bad esn that's why I am curious, its not stolen or anything like that, I just went to a different carrier because I got a better deal on my monthly rate.