Impossible to cancel a Cell C contract

I received an email from Cell C on the 04/08/2020 notifying me that my one contract was due for an upgrade on the 03/10/2020. I phoned Cell C in August to notify them that I would not upgrade my contract but wanted to cancel the contract as my son was leaving for overseas. The consultant said that I can only cancel it a month before it's expiry date so I phoned again on the 03/09/2020 to terminate it. He assured me that it was cancelled and said that I would still have to pay for October. I am still being billed for the contract. I sent an email to customer services on the 24/02/2021 again notifying Cell C that I have had the bank reverse the stop order, they billed me again this month for the total amount and did so i had it reversed again on the 01/03/2021. What is it with Cell phone companies ? They can write you up at anytime and so quickly but you can not terminate a contract even when instructed to do so. I have also had no response to date from the email I sent them. They are pathetic. Only an an automatic reply. They have wasted hours of my time. My time is also money. They will milk you, their customers, to the cleaners but will they give a damn about your wasted time of trying to sort out their inefficiencies. I will never take out another contract will Cell C again and cancel my remaining two contracts as soon as they are due.