Cell C cancellation nightmare

I have had an issue with my cancellations now for almost 7 months without resolve. I had two sim cards delivered to me, this was mostly due to courier issues. The one sim card was cancelled. Then it was discovered that I don't have coverage for the LTE Sim that I ordered. I asked the lady when I app**** and she assured me that if coverage is a problem, I can just cancel the Sim. I have been trying to cancel this Sim for most of 2019. I have never used a cent on the Sim but I still get charge every month, after numerous attempts to cancel. I have been told by customer services that the cancellation is being processed. This was months ago. I am now at a stage where I have given up. The numerous phone calls and getting transferred and holding on the line for hours. Is there any other method that I can follow to have this issue resolved once and for all. Please assist.