Refusal to do a refund on damaged shoes

I bought shoes on the 21/03/2016. Wore it three times then the heel depleted. Went into the branch to find out if I can't get it changed for another one. I had the slip that shows my card had been the purchasing card and went to the same cashier who processed the purchase. I find this irritating that now I'm forced to keep a shoe that wouldnt even last me a week after purchase. It's not like I bought it on sale. I want my money back as this is clearly a quality issue. The manager refused to refund me. Told me straight I need the 2 slips. I can even draw up a statement that proves my purchase. Both the cashier Vegan and Stephanie the manager gave an attitude because I'm not happy with the product. Your staff really needs to be trained proper customer service.