Bad service that i got from jet

I have bought a jacket at jet it was on sale but when I get home it was small so now I went to change it back but they refused saying that the sale items cant be changed how is that possible because this thing is small what am I going to do with it if I cant change it. I still don't understand why they refused me to take another size just because the item is on sale please assist because even their customer care is still not responding to me about the matter ever since last week. I am so furious with the service I got from jet store Bloemfontein CBD.