Incorrect item delivered

I am so disappointed in the customer service I have received from Superbalist. I ordered shoes and on delivery it was an incorrect item. I contacted Superbalist and I was told that the correct one is out of stock and all I can do is request a refund or wait 30 days for the correct item to be in stock again. Today is three days before the return expiry date and that item is still not available. I phoned in and was told there's nothing they can do. This to me is false advertising as I didn't get what I paid for and they should fix their mistakes and get the item I ordered from their suppliers or make an alternative that suits me. I have been ordering from them for four years and their appreciation for my loyalty, sucks if they can blatantly say there's nothing they can do about it.