MTN IS THE PITS

I have for the last 8 months been trying to get MTN to remove an amount from my bill that iI paid in August 2020. I did an eft and my payment was one day late. I have been speaking to 24 different agents which I have emailed the proof of payment to and every month it is still on my bill, MTN then cuts my line I have to send proof of payment again and so it continues. Now i am due for an upgrade but i cant do the upgrade as I am in " arrears" and have to make payment arrangements. Really!!!! Does MTN have a competent person that can actually assist me.