Product on Promotion but no stock

I have been trying to purchase a portable air conditioner from Makro for more than 2 weeks now, but none of their stores have stock. Their website claims there is stock, but when I go to the store they say I must come back later. I've been phoning at least twice a week, not only Centurion, but also Silver Lakes and Woodmead, and all they can say is that I should try again later. How can you advertise something and not be able to deliver?