Cell C poor customer service and experience.

I had a contract with Cell c from July 2018 to July 2020 where I was paying R200 for 10G data. I completed the contract without skipping any pay. In August 2020 the contract ended and cell c kept on debiting me.

I called the customer service and spoke to them that I am no longer interested in the service. They gave me some promotions and I refused. These people could not take a no for an answer and it was so annoying.

Now Cell C continued the contract without my consent and they want me to pay for the service that I did not use. Can cell please clear that debt and I can't have a bad credit record for their negligence and poor service.