Mtn steeling money again.

I have an account that settled and closed a year ago. When I closed the account o had it changed to prepaid. They refused to change it to prepaid until I had settled in full. When I settled I still made sure I over paid so they can’t say I owe them anything.

They are still sending me invoices a year later. That that number. Is a small amount but it’s getting bigger every single month. I have called in every single month for the last year. Each time I get the same damn answer. Sorry about that sir I log a complaint and they will sort it out. But each time same day I get a message saying issue was resolved only to get another invoice next month. Now I call in and the lady tells me. Sir I advice you to pay that amount and settle it. I explain that I had a 9 rand positive balance so How can I be on a negative number a year later after the account was closed. The lady then says the system does not make a mistake I owe them money. Mtn are trying to ***** from me. You guys need to sort this out now. I am getting tired of calling in every month so sort this out. It went from we will sort it out to sorry you need to pay. This is your ***** up so fix it and stop trying to steel money by me by making me pay you. You guys owe me 9 rand. Go look at my account payment history and open your eyes and you will see.