[Q] Phone Unlock Codes

Sorry if this isn't considered the best place to ask, but the forums are rather large.

My friend has purchased a Samsung Exhibit II recently, and he needs to purchase / obtain (legally) a SIM Unlock code for his phone so that he may use it on AT&T.

I was wondering if anyone has had any experience with unlocking this phone (free if possible) and / or know the cheapest / best / most reliable / safe site to purchase an unlock code from.

Thank you all