It's rude to cancel an appointment without sufficient notice.
James has an appointment with his realtor this tomorrow afternoon.
James wants to cancel the meeting and reschedule for later this week.
James calls his realtor firt thing in the morning the day before the appointment.
James waits until the last minute to try to cancel and reschedule the appointment.
The realtor thanks James for letting him know in advance and sets a new appointment for Sunday.
His realtor gets upset, explaining that he could have lined up another client if he had time, and then refuses to reschedule.