Cancellation nightmare

I had a contract with Telkom which was,supposed to end in February ,2020. Like any other contract you have let them know in advance to stop the debits. They just carry on with debiting you without any service. I phoned and did the cancellation online as they requested. You can't go to the shop as they tell you to do it online. Just yesterday I received another invoice. The agent on told me that she can see on the system the contract was cancelled. Nothing has been done to stop the debit orders. Please investigate this for me??