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.
(..) Their mysterious seasons! The moon! Glenn Close! Sheila Riston! All the different kinds of women. Smashing! Oh my appointment. I've got to go and see the psychiatrist. I can't believe there's a psychiatrist in the building. All because those two from accounts just had enough of everything (..)2006 TvShow: The IT Crowd Title: Aunt Irma Visits Season: 1 Episode 6