Eugene,
Was the phone bought from AT&T at full price or contract? If it was full price, there is no need of knowing anyone who can unlock, you just call AT&T and they factory unlock.
There is no other way of doing 'factory-unlock' for the iPhone 4S.
The only method that would work would be to use the Gevey SIM unlock method, which is not a factory unlock.
And what where you doing with the phone anyway?