Billed for itemised biiling that i never received

I had requested that mtn send me my itemised billing for a period of 12 months from 01 march 2012 to 28 February 2013 for tax purposes, but after I was promised that my request would be actioned within 7 day I found myself waiting three weeks later, and the reason I had needed the documents had passed. so I called mtn and made a cancellation to my request since It had not being actioned yet. I was surprised to see that I was charged for the monthly itemised billing X12 that I had requested and cancelled without receiving it. after countless phone calls to mtn call center and even going to mtn branches I still have not received my refund, everytime I fone the call center im told a new request has been sent to the billing department to refund me, but till today 2016-01-18 I have not received any refund from mtn. this has been ongoing for more than 10 months now. my last reference was *** with request no ***.