You can return it. It is illegal not to return it. If you promise a refund, you must pay attention to the refund period and make it within 15-20 working days for the other party to make a promise.

Legal basis:

Article 585 of the General Principles of the Civil Law of People's Republic of China (PRC) * * * The parties may agree that if one party breaches the contract, it shall pay a certain amount of liquidated damages to the other party, or they may agree on the calculation method of damages for breach of contract. If the agreed liquidated damages are lower than the losses caused, the people's court or arbitration institution may increase the liquidated damages at the request of the parties. If the liquidated damages are excessively higher than the losses caused, the people's court or arbitration institution may appropriately reduce them at the request of the parties.