What should merchants do if they are forced to spend?

If the negotiation fails, they will sue the court for fraud and demand to terminate the contract.

Contract law of the people's Republic of China

Article 54 One party has the right to request a people's court or an arbitration institution to modify or terminate the following contracts:

(1) Due to a major misunderstanding;

(2) obviously unfair at the time of conclusion of the contract.

If one party leads the other party to conclude a contract against its true meaning by fraud, coercion or taking advantage of others' danger, the injured party has the right to request the people's court or arbitration institution to modify or cancel it.

The people's court or arbitration institution shall not revoke the request of the parties.