No sense

I took a pair of sneakers which I purchased for my fiance as a gift back to exchange them for a smaller size and due to me purchasing them close to Black Friday, I was now charged the full price on the sneakers due to it no longer being marked down. Surely if you are exchanging an item for the exact same item only one sizer smaller and you have proof of purchase then there should not be any additional charges or am I misunderstanding how the retail industry now works? If we had exchanged it for something completely different then I can understand paying a difference but not with a straight swap. The client services also are not much help as they say it is the shops decision. Surely if you belong to a group then the protocol should be the same for each shop/franchise in that group is it not? Not happy at all!