Unauthorised debit order

Telkom is debiting my account with an amount ranging between R1000 and R4000 every month for a cancelled contract ***7A. I signed the contract on the 6th of Febrauary and cancelled on the 13th February. Between the two dates the devices they gave me were not working and I informed them and they gave me case number - ***4. I then decided to cancel the contract because it does not help to pay for the service I did not receive.<br> <br> Please help me solve this case.<br> <br> Regards<br> Lettia