'Item In Stock' - load of rubbish!

Fed up of websites offering stuff for sale, only for them to cancel the order a week later as it's no longer available from the supplier. First Asda Electricals did it to us with a fridge freezer, now Debenhams Electricals have done the same with a LCD TV. We have already bought the TV stand to go with it from another retailer, changed our plans and taken time off work for the delivery this week. Why do they advertise stuff if they aren't sure it's in stock??? They have also refused to give me a discount on an alternative item so won't be shopping there again.