Coles Supermarkets Australia

The wentworth point store manager (Daniel) refused to return an invalid size of coffee capsule.
I brought a coffee capture which is too large to my machine, they refused to refund or exchange even I haven't used it.
I am so disappointed. Will never go back there again.
I think they can write off the item. what makes them so difficult to do it. it is only 5.5 dollars