Pathetic Dischem policy to exchange item

On the 3rd of August, i purchased 2 face masks (or so i thought) from Dischem Amanzimtoti. When i got home i found i had purchased the incorrect masks as they are for sporting activities and don't have ear pieces. The masks were packed in plastic within another plastic bag. The inner plastic bag that housed the masks was not opened. Today (4th August) i went back to Dischem Amanzimtoti and was told by the Manager that even though the plastic was not opened, they cannot exchange the masks for another mask. He then proceeded to point out a small sign by the masks; pointing out they can't exchange masks once taken out the store. I can fully understand if the entire packaging was opened, but surely if the mask packaging was not opened, Dischem could exchange it for a person. I am a loyal Dischem client but will no longer be using them due to the experience i had today with them.