ADT Security still charges customers after cancellation of service.

I have cancelled my service 01 October 2022 , completed the form and send it 3x because they continue o email me a statement and still charging and billing me post cancellation. I resent them on 20 Feb 2022 o Marlene Du Plooy and nothing was done. I send it again to Dineo Kekana 0n 22 December 2022 and again nothing was done. I honestly don't know what to do anymore. I refuse to pay for any billing post October 2022 because notice of cancellation was submitted. The fact that , they have not processed the cancellation should not be my issue or problem. All i am asking for is that someone must do their job and process my cancellation and reverse all charges please. I still have the copy of the cancellation form completed and submitted 01 October 2022.