MTN is the worst service provider

I am at my wits end with MTN. I have been trying for months now to change the banking details for my monthly debit order, but no luck. I have made numerous phone calls and everytime it is confirmed that it has been changed. I’ve been to visit an mtn shop in cresta (which was a terrible experience by the way). An email was sent and i was promised that it was now sorted, but again now this month it went off from the previous/wrong account. I’m furious and want to change provider now. If there’s anyone that can help please????