Although the name is a prize, this kind of prize is based on the purchase of goods by consumers and is a way of promotion.
I think there is fraud in the shopping center. According to the Consumer Protection Law, the shopping mall can be required to double the return.
You can negotiate with the mall first or solve it through the coordination of the Consumers Association. Really not, it can be solved through litigation (joint litigation with other consumers to reduce litigation costs).
I hope my answer can help you.
Your friend, lawyer Zhao Li from China Criminal Defense Network.