Slops not comfortable, hurts me, wont refund

I went to shoe empire on the 14th Feb 2016 to get a pair of slops, when trying it on in the shop they were fine. But today when i started wearing them after about 30 mins they started to hurt my feet, it started to take the skin off my feet. So i went back today to take them back and ask my money back, but the young guy there with the blond hair told me there is a mark on the bottom of the slop and thus can not take it back as he is not able to resell it..... why would you resell a product that is going to hurt someone els? That does not sound at all like customer care after sales service to me. I was really shocked when the guy told me this. Really disappointing service and you have lost me as customer. That guy had one hell of a attitude towards me, asking me if i would buy a 2nd hand slop. When i asked him what must i do with the slops i'm not able to wear, the response was \not my problem\" WOW!!!! Shocking...... "