Unlocking AT&T Iphone

Do those Iphone 5 unlocking services work 100% of the time for AT&T phones?

I was going to buy a phone, but need to know that the unlocking services work.
It would be an Iphone 5, Clean everything and all that...

Anyone have any experience with these?

factory unlocking services work.... the other that includes sending you software... etc are all crap..