Unauthorized debit order

Completely disappointed with your call centre agents. I very specifically called in May 2024 to cancel my medical aid and advised the agent that cover should end in June. I am billed in arrears which means last payment should have gone off 1 July. To my unpleasant surprise, this morning I wake up a debit off going off from discovery. This unauthorized debit order has now meant that my other debit orders have bounced. This is just unacceptable.