Ombudsman details relating to Telkom

Good day

I am needing to get in touch with the ombudsman with regards Telkom as they have now blacklisted me due to their error.

I cancelled my WiFi with more than enough notice, sent the correct docs and paid all outstanding balances. They still proceeded to invoice me after me contacting them to stop.

I was then handed over to debt collectors and the cancellation documents and emails were sent through to them as proof.

They have come back to me stating that Telkom has credited majority of the amount they were trying to claim but I need to pay the small remaining balance which includes interest from their mistake.

This is ridiculous as this is Telkoms error and not my own.

Please advise