Pathetic service

2 weeks ago I bought sneekers for R300 at Menlyn. I misplaced the slip and I went back to exchange the sneekers for a R300 dress at Centurion mall. I was told that the sneakers are now going for R150 and since I don't have the slip I have to pay an extra R150. I told them that I used my bank card and I can give my statement for them to trace the transaction. They told me that there's nothing they can do. This is such pathetic service because they know that these shoes were R300 2 weeks back. I wasn't there for a refund, I just wanted to exchange the shoes which were clearly in the same condition as they were when I brought them. Someone should get back to me regarding this matter as I want to exchange for the same value. My number is *** or ***.