Contract cancellation not processed as was requested and refund for subsequent billing not paid

I took up a Cell C sim only deal contract with Cell C on 30/09/2020 and a few weeks later I called them to cancel the contract. However it seems the cancellation was not processed as on 28/11/2020 I noticed a bank notification for the payment of R599 to Cell C. So I was still getting billed for this contract. On 03/12/2020 I again called Cell C and the agent confirmed that the contract was still active and he then had it cancelled with immediate effect and I requested a full refund. I insisted on the refund due to the error on their part for not cancelling the contract initially as I had requested in October however to this day I have received no further feedback or money back from Cell C.