MTN KEEP ASKING FOR MONEY THAT HAS BEEN PAID

I am very displeased with the service I have been receiving from MTN for the last year. Every month going back to May last year i have been receiving sms's from their company advising that my services will be cut due to non payment on the account. Even after I make their payment religiously every month by the 1st of every month. I have been informed by the "service champions" this is due to my account being COD and not on debit order *(i cancelled the debit order as they did not run their debit order ontime and then cut my line) and therefore I pay by eft every month. When this reason became overplayed, they started telling me their billing system has changed, which still makes no sense to me as it is not clear why their billing system changing is causing my account to be in arrears and for two months in a row now I have been asked for the same proof of payments from Oct 2020. Which I have provided every single time. And yet again, I am being informed that my services will be cut due to non payment. Even though I paid their account on 27 Feb and sent them the proof of payment. I am constantly having to deal with the same issue every month and no one is resolving this issue. I am tired of the poor service I am receiving from MTN and the lack of effort to resolve the problem on their side even after all proof of payments are provided every single time they ask for it