HI, new to this site so i am unaware if this post may be somewhere else, but basiclly what i want to do, is buy an iPhone 4 (or iPhone 4s) for ATT, one who has a bad ESN, and then unlock it with tmobile. Is it possible to do so?
My particular field of expertise is iOS Jailbreaking and Unlocking.
The only way that a device with a bad ESN can be unlocked is through a backdoor unlock. We, however, do not support backdoor unlocks and they are borderline illegal and in the gray area. Just putting the idea out there for your own use and risk.
Backdoor unlocking isn't hacking. Backdoor unlocking is an illegal method of implementing your device into the global whitelist to be used with all networks even though your device has a bad ESN/IMEI. There's a clear difference