Bad service by MTN

I took out an MTN home WiFi contract for R499 per month. The contract was taken out in September 2020 and on Friday, my account was *******ly debited with R628.97 instead of R499 per month. I phoned MTN and they could not explain. Phoned the MTN Bluffs Store in Durban and they will wait for the agent to return from leave. This is unacceptable. Surely someone can give me proper feedback. I am highly dismayed with the service all round.