Bad attitude and argument with exchange department

On Thursday 16 July 2015 around 18:30 after work I went to Edgars to exchange pajama pants for a new pair that I bought on Saturday 11 July as there was a hole in them. I bought them as part of the buy one get the cheapest one free special. I tried to change them at cresta on Sunday 12 July but they did not have stock. After waiting in a queue I was met with a cashier with an extremely bad attitude. The pants had reduced from R159,95 to R109,95 so I paid for it at a much higher cost but that's fine i just wanted an exchange for exactly the same pants. She advised me that I would need to pay in R25 as I only paid 50% the week before. An argument ensued as I insisted that I didn't owe money as it was a direct exchange and I paid for it at a higher cost the week before. She rolled her eyes and called the supervisor to authorise the transaction. Edgars owes me money as I got the cheaper top of R149,95 free and now the pants are reduced so I paid R159,95. She could not understand that this was a simple exchange and it was such a cheek asking me to pay in for something I already paid for. This was a great inconvenience and I walked away fuming. This disgusting service shocked me