Okay - upgraded and bought an iPhone 4 a couple of weeks ago. Then my brother gave me his iPhone 4S. So I took the SIM card out of the iPhone 4 and put it in the 4S. Sold the iPhone 4 on Amazon, but the buyer wants to know if he can unlock it for tmobile. There is no SIM card in it, but is the phone itself still under contract? Do they contract the IMEI number therefore not allowing for an unlock until out of contract? Is this true? Or once you remove the SIM card, does that mean someone can unlock it? Please help! The buyer is asking for the IMEI number, but I am hesitant to give it out until I have the money in hand. Thanks!