Early termination gone wrong

I am desperate for help. MTN gave me an instruction concerning an account I wanted to close I follow every step and paid what I was quoted 25 November 2020. And the account was closed. A month (31 December 2020) later 10x what I paid was debited from my account. I reversed and contacted MTN and they said it’s a cancellation fee; I was like no way I was quoted R228 and I paid it, now where is the R2233 coming from. They said they will investigate again 31 January they debited me; I reversed. I called them and I explained and the admitted their employee didn’t follow the right way to close an account they asked me to forward the quote and I did they promised me to escalate the matter and they suggested I switch off the pay by debit order and I did. They never came back to me I tried Facebook giving them the reference nothing nothing yet they have now handed me over to legal and I have 2 default record in my credit record for the first time in my life. They ruining me for their own admitted mistake. I want justice now.