Hey, i know its a long shot but someone may have been in the same boat as me before.

Just bought a phone off trademe (samsung Eternity) and need to unlock it to get 850band, its orginally an AT&T phone.

Done the homework on how to unlock it, just need someway of contacting AT&T (cannot register for an account as i am not a customer) to get the unique code to do so, has anyone done this before, or can telecom supply me with these?

Email AT&T perhaps?

you have to have an account to do so, which requires you to be a customer. stupid system really

Check dealextreme - they had various cellphone unlock utilities that were reasonably cheap.