Hi, You can try unlocking your iPhone through AT&T. If you are not successful in unlocking your iPhone 4 through them, You can try with any trusted private source to unlock it. For example, You can visit Simpleunlocking.com to get your iPhone 4 unlocked using remote unlocking service. This method of unlocking is safe, simple, affordable, quick and permanent. It doesn't require a jailbreak too. Good luck mate.