Continue with contract whilst it ended

I entered into a 2-year contract with Telkom during January 2018. That contract came to end during December 2019 and when I visited Telkom's offices in January 2020 I was told that the contract continues unless I stopped it. They further wanted indebted me for another 2 months and now that reflects as a negative on my credit profile. Telkom is a horror show. I did not even make use of the service as I had a new Wi-Fi service provider as of from January 2020.