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.
(..) - This is my son, Christopher. - Hi. - Hey, Christopher. - What are you doing up here? - I came to apologize... - ...for missing our appointment. - You didn't need to come up. We were in the neighborhood visiting a very close friend... ...and I wanted to take this opportunity (..)2006 The Pursuit of Happyness
(..) Rachel, get Ristuccia on the phone for me, please. - Hi. - Hi. I'm Chris Gardner. I have an appointment with Mr. Ribbon. Oh, you just missed him. Thank you. - What's that? - Just filling out a check... ...paying some bills... (..)2006 The Pursuit of Happyness