Mtn ******** more than double debits me

In November 2019 Mtn took it upon themself to debit my account with the amount of R46, and credit it with R474. Then reverse the Credit. Come December I am now liable for more than a double debit because of Mtn mistakes. I have been with Mtn for many years and never have a I experienced such terrible service. No one has even contacted me only via email. This is not my fault and I will not be liable for a double debit due to mtn error. I am going to reverse the double debit and pay for what I signed for. I am truly disappointed!