Telkom still charge me even though line is cancelled

On 2 October I completed and send in a line cancellation form. On 2 November my line was disconnected. On 8 November I get a full invoice and the debit order went off end of November. Now on 6 December, got another full invoice for the full debit order to go off end of December. How can Telkom still charge me for something I do not have! When I phone the affected number it say's the number you have dialed does not exist. Posting it and complaining about it on all social media channels doesn't help or doesn't get any attention. Next step cancelling my debit order at bank, but afraid they will blacklist me for non-payment.