Credit that is not cleared

I was behind with my payments and my credit was handed over to debt collectors I paid R14600 last year around April. They gave me a paid-up letter. I waited forthem to clear my credit score. I waited until August 2025. Nothing I tried to contact MTN; they gave me a second paid-up letter, but it wasn't fixing my credit score. I tried to communicate with them, but they told me to wait their team is still busy solving the issue. Its February now but the problem is not solved it still show that I owe MTN R14000. It's affecting my credit.