How can a cell phone from T-Mobile be unlocked so it can be used on Cingular network?

Please, please don't. This phone was programmed for tm, even if you do get cingular to work and tm to unlock it for you, in will you nothing but headaches, especially with cingular.

The biggest reasons why, cingular roams a lot, and even though with their phones they don't charge roaming, you are gambing with the huge chance of being charged roaming because with the unlocked phone it will not know if you are home or not. It will mostly likely think you are constantly roaming.

Also because it thinks you are roaming all the time your digital services will go funky, texting, voicemail, caller id - all of it.

So please, please don't.

Take it to a phone shop (not a major network owned shop, I mean your local Asian type) and they will plug it into a laptop and re-code it for about £5 / $10