Product on sale but not in stock

They advertise products that they do not have in stock( both at the warehouse and store).

I went there to buy a Defy fridge that is currently on sale and I was met with the "we do not have it in stock so, we cannot sell it to you. But it is there on your catalog, running on this months' special, I too never learn after the disappointment I experienced with the stove that was not in stock but they proceeded to sell.

Also, why advertised things that you do not have?