Debit order after contract cancelled

I have a wifi router contract with Mtn where i pay 240.00 pm and the number is ***. I paid 800 to MTN on 18 Sep 2020 for cancellation of the contract, they confirm on 09 Oct that the contract was cancelled and the SIM card is now on prepaid. I was told no debit will be deducted but on 15 Oct there was a debit order to the 210.00 from MTN, on 16 Nov there is now another debit for 1122.00. Why am I debited the amount whereas the contract is long cancelled. MTN.billing department I am sure you are all Satanists cause you do evil things