How to unlock for cheap a iPhone 4s from at&t?

I purchased a iPhone 4s like a month ago but i not able to use it on my phone company. I have T-Mobile i want to get it unlocked so I can Use it on T-Mobile. I went to the store they unlock phones. They are charging me $80. I'm really low on budget this month so i didn't want to spend that much. Hopefully there's other choices. If not i guess I will have to pay that amount. I called T-Mobile today they said i would i have to to At&t so they can unlock it or something. I really didn't understand them. Please help me. What advices, suggestions on what to do, or what place / website to go to?

Get your iphone on Net10 Prepaid its $50 flat and you won't need to unlock your phone just jailbreak(5 min process) plus if you want to use it with T-mobile you will only be able to use Edge internet speed and there's bound to be issues with picture messaging. Net10 uses ATT's towers so you won't know the difference in quality/speeds but you will notice its a fraction of the price!

You can unlock your iPhone 4S either through AT&T or through any private sources. I would suggest you to go on with remote unlocking service. This method of unlocking is safe, simple, affordable and quick. You can get the remote unlocking service for an iPhone 4S from http://www.classicunlocking.com/apple-iphone-4s/rs16wp9/ with easy unlocking instructions. This method of unlocking doesn't require a jailbreak too. All the best mate.