I bought a car with a trade-in from BNA in August

I bought a car with a trade-in from BNA in August. Received the car and everything was good until I received a invoice from my bank for the car I traded in. The car was never settled with the bank. Now I am not getting any answers. I have to pay for 2 cars. Their response is just we will reimburse you. That car is still active by the bank on my name. No one can give me an answer as to why the car is not settled yet. I would really appreciate answers.