Telkom still billing me after I have cancelled

Hi Telkom, Please respond to this l. My account nr is ********** 62. I have sent teo cancellation letters to telkom via email and have not had a response but have received my bill for this month. Please could telkom reverse this debit order as I have cancelled my subscription and have proof of this. Please reimburse the debited amount for the month of December. I followed the instructions given to me by your call centre. Please answer me. Thank you