Customer service email?

Attached is a email I received which does not allow me to respond therefore I am sending this to your department. The "UNLOCK" code I received from a previous email sent from AT &T does not work. After talking with numerous people at AT&T they were suppose to resolve the issue. The phone I have was purchased under a contract with AT&T which I had completed the obligations of that contract several years ago. AT &T is the company who put the lock code on the device and upon completion of my contractual obligations should remove the locking codes. I have paid for the device in full in accordance with the terms and conditions of the original contract therefore there is ZERO reason to hold my PROPERTY hostage. The mobile phone number is incorrect in this email even though the IMEI is correct. The current reasons reflected in this email does not even apply to my conditions. It is unbelievable that something as simple as this should be requires 4 days and numerous calls to get absolutely NOWHERE. Please forward to me the physical mailing address to the individual or department in your company who I can file a formal written complaint.