My husband cancelled a fibre contract in August 2020

My husband cancelled a fibre contract in August 2020. I have proof of acknowledgment of cancellation by email. Over the past 3 years they have made him pay over 5 times saying it’s not cancelled (over R2000 in total). Each time he pays they promise it will cancelled. They then keep sending zero statements, the latest one being end July 2023. And still not cancelled!!! And now they hand him over to NuDebt who is threatening legal action. We have gone in store to Cell C on 3 occasions. We have emailed. We have spoken to dozens of call center agent and supervisors and told the problem to the people who call saying he owes. No one gets it. We tried to explain to NuDebt too. We have it all on email. Cell C should actually pay us back. Beyond frustrated. Getting no where.