stock is never available

BP filling stations are running a special where if you fill fuel they will give you a free F1 Car. i have filled my fuel and received the code to receive the free F1 Car, however every time i go to the filling station they always are out of stock.. This is unacceptable as they keep saying they dont have stock for the past 5 weeks now. How can you run a special when you dont have the products to give the clients. I filled the fuel and now i want my F1 car