Very bad service

My boyfriend had bought me a dress but was too big, I had tried to do an exchange it at the adderley street branch without a slice but the tag was still on it. When I got there they employee at the till advised that they would ask her supervisor or manager if they can assist as there was a small black dot on the dress which my boyfriend bought it with that dot. The supervisor/manager agreed that I could be assisted, they are which brunch I bought it from and I mentioned canal walk, they asked what I bought the dress with and I was not sure as it was bought the first week of September and they advised that they are unable to assist as it had that dot and I had to go back to canal walk. I had asked the supervisor if this was part of their policy and she said yes, I asked if she is sure and she said yes. I am really not happy with how I was treated because I'm sure they do not check everyday if the clothes don't have dirt on them at the shop for them not to be able to assist me because of that small dot, this is a huge inconvenience as I work in cape town and I now need to go to canal walk just to exchange a dress that they might have at their store😢😢😢.