Incorrectly Billed - unable to resolve in 9 months and still going....

I had renewed my contract in November 2020, when I received by bill I see they incorrectly charged me a migration fee and they have been billing me incorrectly. I opted for the Sky package at R1799 pm which is the amount I have been paying since I upgraded every month. From February 2021 I have been trying to contact the MTN customer support logged numerous calls to resolve this and now almost a year later I am still being billed incorrectly every month. And the cherry on the cake is that they decide to hand me over to some attorneys for an amount I dont even owe!!! Now this is affecting my credit rating which is completely unacceptable and just a waste of my time.