“There are two subscribers, Party B, but only one subscriber signed and confirmed at the back of the contract” will not invalidate the signed subscription letter. According to legal provisions, if the house number, house area, and price are clearly specified in the subscription letter, it should be deemed a contract. If you want to terminate the contract, you can only follow the specific provisions in the contract to see if the developer has any breach of contract that leads to the termination of the contract. If not, you generally cannot ask for a refund of the deposit.