Pick n pay clothing website and the system does not show what os on the store

On the web site pick n pay clothing are addvertising clothing that they say the stores have and then you get to the store. And they check on the system and there system shows they have stock but then the store cant help you as they do not know where the stock is. They might call you in the next two days. We went from mall @reds and they check on the system and they say centurion mall has stock. They phone the store to tell them we are coming to get the dress. When we get there they check on the system and it shows they have stock but they can help us as there is 100 boxes and the dont know which box. And it will take a day or two. So why is it on the system and on the website???