Welcome to Android Forums, Hugol.
I would be very wary of any site that offered to provide you an unlocking code for a fee. If you want to take a phone that is out of contract to another service, your carrier should be able to provide it for you. If you are still under contract with a locked phone, you will either have to wait until your contract ends or pay the cancellation fee.
There are ways to get unlock coded for contracted phones, but that's a violation of your agreement with your carrier so we really can't support or condone it.