Bad service

Bad service, I cancelled a car i sold 3 weeks ago, we agreed on a transfer of unit to a new car which amounted to R800, to that I haven’t received feedback from the cancellation department and today collections department called me telling me i have an outstanding amount overdue of the old car. Agent handling my case is andile maqhubela ( didn’t want to mention his name but I’m angry now because of the service) each time i call I can’t get hold of him and he does not call back. I’ve been making follow ups for 2 weeks now still not assisted