Credit update

I had an account with AMC which was fully paid in September 2021. I received paid up letter from them. However, on my credit report, AMC shows that I owe R1500. Every time I call them, I keep getting transfered from one person to the other. This is really upsetting because I need my credit score updated ASAP as I'm planning on getting big credit. This is so unfair because I did my part, I paid my credit in time. Please fix this mess!!!