MTN does not want to clear my debt even after producing paid-up letter from MBD and proof of payments

My MTN account was handed over to MBD, I paid off the account with MBD on the 9th of October 2024 and MBD gave me a paid-up letter on the 10th of October 2024. I have been sending MTN the paid-up letter and proof of payments but they're not acknowledging it, they say that I still owe money to MBD while MBD has said that the account is closed and paid off that's why they gave me the paid-up letter. This issue is really affecting my credit profile as it still shows that I owe MTN R20397 while I have paid MBD R21193 of which the last payment I made was R18193 on the 9th of October 2024 but MTN says I owe R18397 of which is the same money I paid MBD. I have been calling MTN being told different stories and being sent pillar to pillar, I have even sent emails to them of which are fruitless, I have spoken to the legal and collections department at MTN of which they say they will escalate the issue but with no answers it's been 5 months now battling with this issue.

I have tried to dispute it with Experian of which they have failed, I need advice on what to do because it seems that they're doing this on purpose or they clearly cannot do their job or are lazy and ***********. Should I reach out to Council for Debt Collectors for MBD and NCR and ICASA for MTN as I have reached my limit with this issue, I will no longer be taking any contracts with MTN or even suggesting them to anyone else, I had faith in them but it has slowly faded.