Cell C refuses to cancel my paid-up contract

My 24 month contract with Cell C ended in April 2018, whereafter my contract would continue on a month-to-month basis. Beginning of March 2018 I telephonically contacted them to cancel the contract when it ends and was told my request has been processed and that my last debit order would be on 26 April 2018. On 26 May 2018 Cell C debited my account and when i called to find out why, whereas my contract is cancelled, I was told there are no records of such a call or a request. I was furious but nevertheless went through the cancellation process again with yet another consultant. He reassured me that the instruction for cancellation had been processed by him and my account would no longer be debited and that the call is recorded. I asked him what to do if Cell C debits my account again and he again re-assured that it would not happen as he has processed the instruction to cancel. I had so much faith in him I did not even ask for his name or the call reference number. Guess what? my account was debited yet again on 26 June 2018. This time around I did not even bother to call because calling Cell C is a waste of any one's precious time. I reversed the amount and blocked them from accessing my account. Cell C is a rip-off and an inconvenience and I want nothing further to do with them.