Extremely bad trade service

I traded in one of my cars in December 2021. When I went to renew my license disc for my other car in October this year (2022), I could not because the ownership of the car that I traded in has not been changed by BB nissan. I contacted the dealership twice since I'm stuck with a car under my name that is blocking my other car licenses from being renewed. I have not been able to get any assistance, I am told to send details of the car and then nothing happens after that.