Wors ever experience ever from Telkom

On 31 January 2019 I cancelled our contract, 2 years was up end February 2019. Last payment went off end February. Till today they are still putting debit orders through my bank. I have to go to the bank to reverse the debit orders every month. This month they already put the debit order through twice. I have the cancellation emails that I have received from them. How do I get them to stop the debit orders? Worst service ever, had connectivity problems from day 1 after they sold me contract over the phone, telling me that I get 3000 minutes to any network. After we received the wifi router and sim cards we only realised it was only telkom to telkom. Will never in my life make use of them.