Billing for cancelled contract

I cancelled my data contract with Telkom Mobile in June 2015. Telkom refuses to process the cancellation and has continued to bill me every month. I have spent hours each month begging customer service to cancel the contract and refund the debit order. I have also visited the store on multuple occasions to seek help but to no avail. I can not begin to describe the frustration of having spend an hour on the phone trying to reach a representative and explain everything from the beginning each time.