Chevy Trailblazer Radio says locked?

My husband owns a used car lot and he took a CD player out of one Chevy Trailblazer on his carlot and put it in my Chevy Trailblazer. The radio now says locked? He told me that a Chevrolet Dealership will have the unlock code and for me to call them and get it. I called them and they said i have to bring my car down there to them.. Does someone know how to unlock my radio or have the radio code? I have a 2005 Chevrolet Trailblazer.