Exchange size

I went to Rage shoes and clothing to exchange shoes that I bought a week ago. Reason for wanting to exchange is that it was a correct size but because of the design I was suppose to be advised to a bigger size but I was not told. I wore the shoes just half a day and my toes were swollen I couldn't put my feet down. That's when I decides to take the shoes back to exchange for a bigger size. The lady who was helping me at the shop called her manager to check the shoe and she said they cant exchange the shoe that's been worn. I tried to explain the situation to the manager but she did not want to listen. Even on the receipt there is nowhere were it states that no return goods are accepted or maybe no exchange is allowed.