Bad service and arrogant manager

I bought a dress from this boutique only for them to deliver a wrong dress. When I told them that is a wrong dress they told me they thought I would love the dress as they did not have the one I ordered on stock. What surprised me is that on their website they still advertise the dress and the manager told me I can only return the dress at my cost using the courier I paid. I asked him why did he process the order knowing it was wrong he told me some customers love the dress even though is not the same. Now I am sitting with an ugly dress that I did not order unless I pay extra 100rands to courier it for my refund and I wonder why did he send me the wrong dress deliberately as now I am the one having to foot in the extra cost