MTN not rectifying excessive amount deducted from my account in error

I was contacted approx. the 7th January 2022 to upgrade my MTN contract which were due to expire. I agreed to the contract which would provide approx. 15GB day time and 15GB night time data. This new contract I was specifically told would be effective from the 1st February 2022. Approx. a week later when I tried to convert my air time I bought to minutes via the MTN app I continuously received an error message. When I queried this with MTN customer care I was told that the new contract I am on does not allow air time conversion to minutes as I was on the new data only contract, I then requested to revert back to my old contract and where told by MTN that they could not do the revert and it would have to be done by MONDO whom sold me the upgrade. Note new contract became effective before 1st February 2022. I contacted MONDO and requested the upgrade be reversed and immediately noticed that I could again convert my air time to minutes, the reverse was processed on the 12 January 2022. My old contract had a subscription fee of R199, however on the 25 January 2022 I was debited R1434.83 When contacting MTN about this exorbitant amount of money taken from me I was advised to contact MONDO, and ever since the 25 January 2022 even though MONDO acknowledged this was an error, I have been given promises of feedback over and over again but to no avail. I have spent quite a sum of money on calls to MONDO and the impression I am getting is that they hope that I will just let this issue go. I have a list of 5 people I have conversed with on multiple occasions. On 9 March 2022 I requested to speak to the Mondo manager (I have her name) in charge and where told she would come back to me, I am still waiting for the call or for a resolution to my query. When querying this mess hoping that MTN whom I have the contract with would sort it out, they just refer me to Mondo.

Please beware of these companies, even though I have been a customer for 25 years, i am today a very disappointed customer.