We are calling to 'confirm your appointment' with Dr. Jones. = We are calling to make sure that you will 'keep your appointment' with Dr. Jones.
The museum is open to visitors 'by appointment' only. [=you have to make an appointment to visit the museum]
The court ordered the 'appointment' of an attorney to represent the child.
(..) - But it’s what you wanted. Your friendship with Chancellor Palpatine seems to have paid off. That has nothing to do with this. The only reason the council has approved your appointment... is because the chancellor trusts you. - And? - Anakin, I am on your side. - I didn’t want to put you (..)2005 Star Wars: Episode III - Revenge of the Sith
(..) I’m overwhelmed, sir. But the council elects its own members. They’ll never accept this. I think they will. They need you. More than you know. YODA: Allow this appointment lightly the council does not. Disturbing is this move by Chancellor Palpatine. I understand. You are on this council, (..)2005 Star Wars: Episode III - Revenge of the Sith