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.
(..) we are swimming in our own... - Here he comes. - What the...? Crikey. What a state. Barbara, what's my earliest appointment tomorrow? - ., love. - Leave it open. l've got to clean the fish tank before Darla gets here. - You hear that, Sharkbait? (..)2003 Finding Nemo