Unlock AT&T Iphone 5 16GB model

[akhi]

Hi,

I am new to this forum and need your help with unlock of a At&t IPHONE 5 device. Currently I am on T-Mobile network.
In bestbuy, I saw 16GB Iphone 5 for AT&T as 249$(buy as replacement device). Can i unlock this directly without ever using the phone on At&t network using websites like swiftunlocks,etc?

Please help me with this.

 

[akhi]

Help needed

Any one please help me with this query.
Your help is very much appreciated