Return policy

I bought a pair of sneakers at Truworths Westgate and after wearing them briefly I decided the size 7 i took was not comfortable enough. So the following day I returned them to exchange for a smaller size 6 which i found fits nicely. I was told that I can't exchange them because they have been worn already. I had to buy that size 6 because I loved the shoe, and so I'm sitting with a size 7 i can't wear. I'm curious about the return policy when it comes to shoes because it's dumbfounding, can anyone clearify that for me. If that's company policy you guys need to put up big signs on the shelves in stores to alert customers, seriously.