Cancellation of contract not processed

I cancelled a cellphone contract at Cell C on 10 January 2014 at Cell C Kolonnade. The assistant helping me was Elsie Wilson. I paid the outstanding amount on the cellphone (R6940,47), but the cancellation was never processed. I have the proof of payment. I recently noticed that the cancellation never took place. The contract period ended at the end of July 2015. I sent another cancellation request on 15 September 2015, but nothing happened still. On 27 October 2015 I went to Cell C Kolonnade and gave the cancellation request manually to David Rennie. Nothing has happened still. I want to get the contract stopped immediately and get a refund on the debit order from February 2014 onwards.