Is there somewhere I can unlock my iPhone 4s?

I have an iPhone 4s issued to AT&T, I want to get T-mobile on it, however, it needs to be unlocked (not jailbroken). Are there any places that offer unlocking? I'm worried that if I do it myself, I'll get scammed by some website.

If you haven't already used up all of your unlocks, you can unlock it by calling AT&T and asking for an unlock. If you have used up your unlocks, then I guess I can't be of much help.