AT&T can't find my iphone's unlock code?

I called att to get my iPhone on iOS 5.1.1 baseband 4.12.01 unlock and then the person said she could not find my unlock code to unlock my iPhone and that there was nothing she could do?

Why can't she find the unlock code and what else can I do?

You can unlock it through another way of course. I would recommend you try http://iphoneunlockshop.com, it is the places that I use all the time for my iPhones. Basically they give you like all the softwares and instructions that you need for the unlocking of the iPhone.

You can use this service. Very large unlocking opportunities for almost any phone model.