They advertise in store Playstasion 4 (the box is on the shelf)but when you wanted to buy the product they suddenly have no stock

They advertise in store Playstasion 4 (the box is on the shelf)but when you wanted to buy the product they suddenly have no stock. They let you sit at their desk to do the transaction and after about 10 minutes they tell tou that they do not have stock. When you ask them why they still advertise it and still have the box on the shelf, they can not answer.