Cell C does not release optic fibre lines on request

I recently moved and tried to keep Cell C as my SP. When they were unable to connect me after numerous attempts, I cancelled them out of urgency to get WiFi, but they are not releasing my optic fibre line to allow me to connect with another SP. They are basically holding me hostage. They’re not providing me with internet connection but not allowing me to connect with another SP. I have also paid them until the end of February but haven’t got any service for the whole month so far. Numerous emails and calls have not helped. At my wits end. How can one company not provide a service (you’ve already paid for) but prevent you from obtaining that service from another. It’s ******** and *******.