If someone signed a contract with a man to have sex with someone, but?
Yes. People are not property. They do not belong to anyone but themselves and you cannot purchase them like a piece of meat. You cannot put a contract on someone's body and their autonomy over it. They can consent to sell you services, but you do not have any right to their body at all. If they withdraw consent and you continue, that is rape and should and will be prosecuted to the full extent of the law.