Unauthorized debit

I have cancelled all my old mutual insurances due to different monies debited. I even had to switch banks due to this inconvenience. Yet they still continue to try and debit from my old account and now I'm faced with negative balance of over R1000 due to their attempts. ive called old mutual went to the branch even sent an emailed complaint yet the attempts to debit still happens and the frustration is that the amounts vary with each attempt. I would like old mutual to reimburse the bank charges because according to their records everything is cancelled yet im sitting with the very same old problem