Go to official website, talk to customer service, and you may get some money back, or complain or admit your bad luck.

the price difference refers to the futures price difference of different grades, different delivery months, different commodities and different delivery locations. It also refers to the price difference of the same commodity due to various conditions, such as wholesale and retail price difference, regional price difference and seasonal price difference. Some businessmen do business just to earn the difference between buying goods and selling them.