Continues over billing and not cancelling service as requested

I changed my package in June with a new monthly amount of R1270pm. Telkom has changed me R2000pm ever since, They acknowledged the problem for one month and credited me, and then over charged me July, August, September, October, and November.

The best part is, I cancelled the service on 26 September for end October, and they still keep on billing me and don't cancel the service.

I logged multiple disputes with them, and they just keep on rejecting it on the system.

All I want is that TELKOM 1.) Cancel the service (backdated as per my original cancelation) 2.) Credit my account with the overcharge as per our contract that states that I get a gated community discount and correct the invoices.

But that is too much to ask