Feed up client

I had a contract with Telkom and did not renew it but they kept debiting my account every month even two times a month the take plus minus 1500 frm my account. I have called and requests them to stop debiting my account they just promised to look at the matter even today the deduct money which I had to reverse at a cost of 45 rand per transaction. They said the gonna cancel my debit order instruction but nothing was done.which ombudsman can help in this matter as I very fed up with Telkom they messing with my credit score and my business