Please help i want them to stop the debit order and refund mymone back

This company busy debited my account while i cancelled the contract with them. I app**** router wifi in February and it was not working. I Manage to return it back on same month. In March and April they debited R468 each month i manage to reverse it with my bank.,In May they debited R239,June R229,July R936 that bring the total of R1404 i tried to complain with Telkom,they took me pillar to post and they don't offer solution.