FNB service very poor especially when you want to clear your name.

I think FNB has the worst service ever, they handed me over debt collectors which is fine I paid everything according to the agreement and instructions, few months down the line I got a settlement discount from DMC around May 2024 I was given a settlement letter fast forward around September 2024 the account with FNB wasn’t closed, I was told it had payment short, I enquired with DMC and it was paid, now October the 9th I have -R1300 that needs to paid by me, what was I paying for all the time? Who came up with the calculations until they end calling me to make arrangements for the payment? FNB and DMC someone is playing foul play. I need to raise this issue with NCR and Ombudsman. I paid everything that was instructed by debt collector, why am I still liable to pay? Really disappointed with FNB easy to get into debt but not easy to clear your name even after when you paid everything.