very bad and disappointing service

My contract with cell c ended in August this year however they have been debiting my account. When I asked what is it for I was told that it is for disconnection fee as well as subscription fee. Cell C debited more than what they were supposed to for this contract for the whole dutation that I have had the contract with them and when I asked for the extra money they have been taking from me to be refunded, they told me that it was for itemised billing that I never even signed up for especially since I wasn't even using their sim card. Getting assistance from their contact centre is always a nightmare as they always promise that someone who will assist with thr query will phone me on the next 24 hours and no one ever has till this day. I have had contract phones with Mtn before and not even once have o experienced such bad service. All I need from cell c is to refund me all the extra money they were debiting for my contract, claiming to be for the \so called itemised billing"I never received services for"