Cell C continually deducting money for a contract that I cancelled a few months ago

I had two data contracts with Cell C that expired around July. I called Cell C to cancel the contracts once they expire. The call center agent ensured me that the contracts were both cancelled. As months passed an amount equal to one of the contracts were still deducted from my account.

I called again and the call center agent said that they can see on the system that I have previously informed Cell C to cancel both the contracts, but only one was cancelled. The agent ensured me that the problem will be resolved and that they will escalate the issue.

Continuing to December 2018, every month the amount was deducted from my account so I called Cell C again. Again did the call center agent see on the system that only one contract was cancelled. They had to come back to me on the issue because they have to send it to their financial department.

Needless to say, THEY DID NOT COME BACK TO ME.

After I called them again after a few days they informed me again that the contract will be cancelled and that I will be refunded by Cell C.

On this great day of the 1st January 2019 I the amount was once again deducted from my account and no response regarding the issue from Cell C and no refund.

Cell C can you please tell me if you think that you have handled the issue with enough importance and at this stage in an ethical manner?

I have always paid my bills for the contracts that I had with you on time, never missing a payment. And this is how you handle a client that WAS loyal to you.

I, as a consumer, feel that I am paying for your mistakes. If I were to block the debit-order from my side at the bank, then I would get a bad credit rating, because of your shortcomings and negligence.

Please inform me how you would proceed with solving this issue? Who is liable and when will I get my money back?