Unable to stop account.

I am tying to cancel my Telkom line from the 15 September 2020. Yet I only receive emails saying cancelation order number: is in progress. You will receive confirmation as soon as it has been successfully completed. All emails I am sending come back undelivered and some saying please contact us with a phone number for assistance. I received an invoice this morning to pay another month when will this stop as you can not email them or reply on any mails received. I had to pay end September now I need to pay also end October. come on please