[A Passenger Switching to Another Car After Booking]

Question: The owner of a saloon car agreed with a group of men to take them for Ḥajj and visitation for an agreed fare. When the time of travel came, some of them said: “We have agreed with another driver.” Do these individuals have the right to ride with another driver, given that the first driver had reserved places for them, and were it not for this passenger, he would have found another?