Waste of Time V+Card

I was told by staff to register a V+ card at Shell Garage Kokstad to gain points as I always go there for petrol, I always swipe my card to get points and I have noticed that I have points to spend. I went to Shell in kokstad and took some soft drinks when I got to the cashier I was so disappointed to hear that I cannot buy with this V+ Card they do not take it. What is a use of swiping a card everyday for points if you can't spend those points???