No stock on shelves

Good day. I was at pick n pay Wonderpark Pretoria and there was a special on the leaflet for fruit tree juice. As a got to the shelve there was nothing and was told they are out of stock so I carried on with my shopping but when I got to the outdoor area about 5 or 6 staff members of pick n pay came out with trolleys with the juice in a out halfway stacked and so I asked them if I could have some because there is nothing on the shelve they told me no I can't because it's for the staff and not customers. So how does that work? Kind regards