Cancelation of contract but still billed

On the 4 September 2024 I submitted a contract cancelation. I'm not getting any assistance for this instead I am billed monthly with the device not working anymore after the cancelation. I was given this reference number *** ND***. To do follow up the telkom cancelation switch board is not answered, I'm transferred from pillar to post with no assistance. This is the reason I am leaving telkom, their service sucks.