Thanks for the question.
Unfortunatly, on this model year radio, the only way it can be unlocked is through a GM dealer. These radios do not use codes anymore, they actually learn your VIN#. This is what a GM dealer will have to do.
Sorry, there is not an option to turn it off anymore. I know a lot of people wish there was.
Here is the info I have from GM....
The "Theftlock" theft deterrent system is a feature on all base and uplevel radios. There is no need to program a security code into the radio as in past model years. The theft deterrent system now utilizes Class 2 serial data to determine if the radio is in the appropriate vehicle. Each time the radio receives the "run" power mode message, it compares the VIN information it has stored to the VIN information received from a module on the Class 2 serial data circuit responsible for transmitting that information. If a mis-match occurs, the radio display will indicate to the user the radio is locked. Once this takes place, a DTC will set, the radio will not respond to any button presses and become inoperative. The only way to unlock the radio is by using a scan tool.