Absurd Service!

I've recently discovered that cell c claims that I owe them for a contract I paid off 4-5 years ago. A lady called me after multiple attempts of me trying to reach their legal team, and she was the furthest thing from helpful. I proceeded to write to cell c and they sent me a mail on the 19th of June 2019 stating that someone will call me within two business days but I haven't received any communication up to this point. The lady couldn't pull any records of my interactions with them nor the payment I made to pay off the account, which is convenient for them as they confirm receipt of it at the time. She couldn't answer any of my questions and I wasn't contacted by cell c until I attempted to take out another contract with them this year. So as far as I am concerned, the "debt" they are referring to prescribed a long time ago and they didn't even follow the correct procedures in adding a default against my name. I WANT THIS REMOVED FROM MY CREDIT PROFILE!