Money to be refunded after incorrect debit order

On buying a pre-owned vehicle from Audi Centre Northcliff I traded in my existing vehicle to the dealership. Audi Northcliff handle the financing of my new car. A month after taking delivery of the new car a debit order went off my account for the old car which I had traded in. This issue I then discussed with Audi Northcliff and after numerous phone calls and emails I have had no joy and no feedback. It has been longer than a month now and this issue has still not been resolved. I have not even had response letting me know when it will be resolved and what the issue is despite numerous phone calls to the salesman who handled my purchase.