Contract

Good day i had 2 contracts with cell and one of them came to an end and i did not renew it. Ever since then i get calls and e mails from cell c telling me that i havent paid for my remaining contract have called the contracts departnment and been told it does reflect on the system that i paid but still says im in arrears asked for further details and was put on hold for the available team leader then was told she is busy can she have my details so she can call me back. Been waiting for the call only to recieve another email saying i owe them. Same thing happened last month sent them proof of payment still they continued. Cell c this is harassment please and its not nice