Wrongfully debited for non existent contract

My contract came to an end in Dec 2025 and I notified them using the notice period that I will not be renewing the contract, thinking that Nov 2025 was my last debit order month. End of Dec my acc was debited with even few extra rand and when I went to MTN Margate they printed a statement to explain everything and that Dec was the last month of debiting my acc. I was also advised to call their customer care to ask about the extra few rands I was charged. Unfortunately, no one was able to explain and I decided to let it slide. Yesterday to my surprise, MTN debited my account again with even higher amount and this time I decided am not going to let MTN bully me financially and I reversed the transaction and waiting to hear from them because I cannot continue to pay for a service that am not recent from MTN