Unable to get monies owed.

I purchased goods from supplier with gift vouchers, small balance to be paid by me. Later I discovered the full amount was charged despite them taking the gift vouchers. <br> I contacted the supplier and had to prove the use of gift vouchers which was clearly indicated on the till receipt. The supervisor promised to get back to me after speaking to management on how to reverse the payment.<br> After contacting them more than once, still no feedback and I have been asked to contact them or to come into the store to speak to someone. It has now been a week and it seems like they have forgotten about my money.