Bad customer service

I had a contract with cell c fiber for 2 years, after the 2 years has lapsed I didn't renew the contract. I continued with them on month to month contract. On 15th of July 2020 I send an email to c fibre support and cell c customer service to terminate the contract, which cell c respond indicating that the matter is escalated to the relevant department for assistance. However cell c continued to debit money in my account until November 2020 which is four months. To my surprise they are still sending emails that I owe them instead of them refunding me the money they debited after I terminated the contract. I want them to refund me the money they debited for 4 months.