Mr Price Exchange policy is the worst

My mom bought me a skirt for R179.99 @ MrPrice and I don't have the receipt. When I went to exchange it the assistant store manager told me they don't do exchanges without a receipt so I spoke to a lovely agent named Palesa (exceptional service agent) from the Mr Price call center who got them to do the exchange for me. The skirt is now marked down to R80 and I'm being told the refund & exchange policy states that I will only exchange for that R80, which will put me at a loss of a R100. I called the call center and the agent advised it's the store managers decision. I do not feel that it's fair to lose an entire R100 because I do not have a receipt. The Mr Price branded tag is still attached, the skirt was never worn. This is just horrible.