denied the right to a refund

I bought a pair of jeans unaware they had a small stain. I discovered that they were small when I got home. I tried to return them for an exchange at carnival mall but I got told to take them to the brakpan branch where I had initially bought them. I called custumer care and was told that I could not exchange them at carnival as the store manager had said so. I took the same jeans and returned them at the bokburg branch without incident. I was disappointed witbe carnival branch