No refund for data not requested

When I renewed the cel contract, I did not instruct MTN to add 1 gig data as per my old contract, this was an upgrade. Since July 2015, I have been charged for the 1 gig, I did not receive the 1 gig on my phone, but MTN has been charging me for it. I went to the mtn shop where I renewed the contract, they gave me a Ref *** I waited a week nothing was done. I phoned mtn customer care i was given a ref ***, another week passed nothing, I phoned again, I was told it would be sorted ref *** on 12/10/15. No email statement for novemer from mtn I see money was debited from my account, as far as i can see no credit was given.