Company keep billing me for canceled contract

On 09Nov`2014 I filled out a cancelation form from Telkom Mobile for my 8ta contract which expired in Sep`2014 and was no longer in use. The next month I got an invoice again for my contract, so I resent my cancelation form to [Email Removed] I phoned Telkom Mobile again and I was told that it takes 21 days for the cancelation to be processed. I was also told that I must do the cancelation from my closest outlet on which I rep**** that we do not have a Telkom outlet close to us. The operator requested me to please resubmit my cancelation form again to the same address. I probably resubmitted my cancelation form about 5 times if not more. In January`2015 I was billed again from Telkom Mobile for my contract that does not exists anymore, same for February and March. We are now in April`2015 and on the 2nd Apr I was again invoiced for this contract that was cancelled. Telkom Mobile has still not cancel the Debit order from my account! This is the worst service I ever received from any company.