Network Unlocking help?!

Ok, so I am trying to unlock my iPhone 4s for use with family mobile, I am pretty sure it will work with other carriers like net10, but with family mobile it requires unlock code(the same thing that happened to my moms phone). So I have called AT&T like 10 times with a lot of different responses from the reps.

Most said go to AT&T.com/unlock device :

I did that but the emailed me saying to email/fax them a recipt. I brought this phone from a pawn shop so there is no hope for original recipt, will they accept pawn recipt? Is there any way around using a receipt?

One lady told me to go to iTunes and restore from factory default.

I heard of this working before, but only after AT&T emails you, should I do this?(because I just finished retorting my iPhone, and due to my slow Internet, it took like 12 hours.)

Also does anyone know of any unlocking services(online or otherwise) that work for iPhone?

Thanks for reading