MFC Nedbank car *****.

Hi, I requested a settlement for a car and I paid within stipulated time. However, they made a mistake by charging me twice in March 25 and 28. They accepted that it was an error but still I need to pay for that error. I sent hundreds of emails to their complaints department, they told me the same thing. How do I get my car documents from them because I discovered that I was the 5th person who has the same problem with them. It means it was not a mistake but it's a way of exploiting customers.