Non cancellation of services not rendered

Telkom sent a rep to my house to offer me a service of broadband at a speed of 10MBS. I took up the offer during October 2013. However Telkom was unable to achieve the promised speeds ever, Although numerous calls were made the with numerous ref numbers, the best they could do was sending a daily SMS saying that they will be attending to the fault shortly and I would be reimbursed for services not rendered. On 2 December I finally had enough and cancelled the service. I was given a ref number for the cancellation. A month later I received my account only to notice the I had been charged once again for the faulty service. I contacted Telkom from their offices in Clearwater mall. I was assured the charge would be reversed as it had been charged after their close off. I paid the amount I owed, leaving the amount incorrectly charged to be corrected as the operator had promised. In Jauary I received another account. Not only had the previous charge not been removed, but I had been charged again. I went back to the office at Clearwater and raised a query. The ref for the cancellation could be tracked. My latest invoice has still not been corrected and further charges levied!!!!