MTN and early cancellation is the worst!

So i did early cancellation on my contract.They sent me the amount and I made the settlement.it is now more than a month later and they still says the amount is not reflecting in they're account.In the meantime I get warnings that my account is overdue and being threatened. But I always pay every month into that account and even last year I also made an cancellation payment into that registered MTN account with no issues,but now they keep saying the amount is not reflecting.And R20 000 is a lot of money. So I came here to see if I can get assistance here because I am getting bad credit because of someone not doing their jobs