Priv MEP locked with ATT Supplied unlock code at ATT store by store salesperson & ATT tech support

Hi my Blackberry Priv was MEP locked at an ATT store with an ATT store salesperson and technical support person who attempted to help me to unlock the phone. 

My phone was purchased directly from ATT.

Before bringing the phone in to an ATT store, I made two unsuccessful attempts at home try to unlocking the phone.  I then brought the phone in to the ATT store up the street to prevent from locking the phone myself. The salesperson attempted to unlock the phone using the ATT emailed unlock codes that i brought in on my second phone. After several attempts failed, we called into ATT technical services to have them confirm that we had the correct code and walk us through the process of unlocking the phone. We confirmed the codes were accurate and then reentered them while on the phone with tech services and the phone then became MEP locked.

I have called in to receive assistance and was told that there was nothing that ATT could do because the day that i attempted to unlock the phone at the ATT store i also paid off my balance and ended my ATT service. Now i am unable to use my phone with any other carrier accept ATT. I am not very happy about this at all.

ATT has simply said that i should contact blackberry to inquire about getting them to unlock the phone or getting a new phone due to warranty. Blackberry says that they are unable to unlock an ATT phone because the software which locks the phone to ATT is installed by ATT, and furthermore Blackberrys contract with ATT clearly states that ATT should handle these issues. 

I feel that ATT has left me out to dry. I have been a loyal ATT customer using the service for both work and business for over 10 years straight, and I have made the decision to never use their wireless service again unless this issue is resolved. This is my final attempt to reach out for their support.