Volpes refuses to exchange products with factory fault

My heart is so heavy when I think of the treatment I received from Volpes just for requesting an exchange of their faulty product. I bought curtains in January, Only noticed a factory fault last week when I was hanging them. I went to the store to request that they exchange the one that has factory fault. The manager started by measuring them to confirm the allegations. After she realised that I was right, she requested the slip. I told her that I did not think of keeping the slip since I bought the curtains on “non faulty “side of the store. Remember they have a portion where they keep faulty products. Now, I trusted that my curtains were up to standard. Kolonade branch manager treated me, and told me that O was supposed to read the policy at the back of the slip. I left my curtains there, but I still want justice. This is not fair. Contacted their head office, they responded saying I was advised to bring the slip. Meaning, I lost my money. Plz help, cost of leaving is too high