Cell C cancellation of gontract

I cancel my contract on 9 March 2022, via email. But they keep on deducting from my bank account I wrote email again on 25 March, 20 April, 3 June and 4 July. The send a return email that they fid receive my mail, but they don't read their mails What can I do, because it Cost me money to send the payments back every month!!!!