Pre-booked journeys
Booking for a particular time, and how to cancel.
You can book a journey for a time in the future, giving the day and the hour of the pick-up. The same rule holds as for immediate journeys: it is confirmed when a driver has accepted it, not when you sent it.
A pre-booked journey can be cancelled up to an hour before the pick-up time. Some operators set a different limit, and in that case you will find it written on the job. After that point, no: the driver has already set off or has already turned other work down, and somebody really has lost that time.
For a flight or a train, book with some margin and put the flight number in the notes. The driver needs it to know whether it is worth waiting for you when you are running late.