MTN Poor service and support

I have been a customer of MTN for 20 years and have had contracts with them since then. 2 years ago I signed a new contract for R369 per month on a monthly debit order. In January 2019 they started debiting me R399. I complained and in April they gave me a credit for the 3 months, but they did not rectify the fault. Since July 2019 to date I have been billed R408 per month. I complained several times and nothing was done. A month ago I visited the Amanzimtoti branch (Galleria Mall) to try to sort out the problem. They took copies of my contract and forwarded it with the complaint to the relevant department. They contacted me a few times to tell me they were sorting it out and I would receive a credit for all the months I was over billed. I also received SMSes to tell me the query had been resolved, but again this month I was billed R408. My contract is now at its end and I need to sign a new contract. After 20 years of being a loyal customer, this is the service I get. Unfortunately I am forced to now look at an alternate cell phone provider.