Do you want to use your iPhone 4 with T-Mobile or another GSM sim card? If so, we can unlock your iPhone to work with any GSM sim card/carrier so you are free to use your iPhone with another carrier or use it overseas with another sim card while traveling. This unlock will only work on iPhone 4 running 4.x software, it does not work on iOS 5 or later. This is not a software unlock, it uses a Gevey sim transposer to allow the iPhone 4 to work with non-AT&T sim cards.