Always a struggle to get a line cancelled

We had an adsl line with telkom and upgraded to fibre so we needed to cancel our telkom subscription. Firstly we could not get through to their call centre so we went into a shop and they did it for us on the app. This was in September already. They still billed us for Oct, Nov and now Dec. We do owe some money that did not go off on debit order bit will only pay once this has been resolved. We look forward to hearing the explanation on this pathetic service