PROMISED A REFUND BY NOTHING RECEIVED BUT EXCUSES

I have an existing internet contract which expires on 31st March 2016, I was offered an upgrade in November which I accepted but I changed my mind and immediately cancelled and returned the device. I have the cancellation number and waybill number as proof and I was advised that all was in orders. However, on 31st January 2016 Cell C withdrew R554 from my bank account and when I phoned them it was established that they had charged me for the device that had been returned to them. I spoke to several departments that day until finally getting a consultant who together with her team leader sorted everything out (so I thought) and said that Cell C had made a mistake as I had done everything right and that I would be getting a refund within 7-14 days. I have the relevant Package No and Finance No that they gave to me. To date nothing and I have phoned several times only to be told that phone after another 7 days as these things take time, it was being processed and finally today that the Case is Closed. How can it be closed when I have not received the refund due to me. Customer Care generally are not helpful as you just get passed around and fobbed off.