MTN ERROR & bad customer service

I have had a terrible experience with MTN. I was due for an upgrade in December 2020. I only decided to upgrade at the beginning of February 2021. An amount of more than R1200 was incorrectly debited from my account at the end of February due to an "early upgrade". I have called MTN 5 times and even spoke to the manger at some point. I have received bad customer service every time I called. They all read out a statement which indicates that a whole lot of people have been incorrectly debited and it will be credited into my account. None of that was done but rather, they debited my account again in March 2021. I regret going for an upgrade because of the inconvenience that MTN has caused me and failed to return or credit the mistake that they have made. It has been difficulty financially due to economic pressure caused by COVID and MTN does not seem to care or be responsible enough to correct their error but would rather frustrate a loyal customer of more than 12 years.