Cannot exchange Builders Warehouse brand products without slip

Builders Warehouse has always been the shop I go to and that is why I am so disappointed in my experience at the Atterbury branch yesterday. I bought two Builders Warehouse brand sockets a while ago, worth about a R100 for both. I have not used them yet. I decided to change all switches and sockets in my home and decided on using a different brand. Yesterday I went to Builders Warehouse with my list and the two sockets I would now not use.I could not find my slips, but thought there would be no problem as they would know I could not have bought Builders brand anywhere else and the packaging was unopened with the barcoda sticker anditisnot perishablegoods and they would not lose money. I went to the exchange counter and explained everything to the lady and explained that I do not want my money back, because I want to buy different sockets and would accept a voucher to exchange. She just said that if I do not have a slip, she cannot help me. She was like a brick wall and unsympathetic. I was so frustrated I gave her the 2 sockets and told her that she can keep it then, because I don't want them. I went in the store and bought R 4,100-00 worth of sockets and switches. I thought it is ridiculous that I spent so much money at Builders Warehouse, but that they could not even accommodate me with exchanging 2 sockets worth a R 100-00. I asked to speak to a floor manager who did not listen to me and did not care about my situation. She barely spoke to me and seemed preoccupied, not even looking at me. I just left. I am disappointed in you Builders Warehouse.