If you want to make or book an appointment you can use these expressions:
What about ….?
What about next Friday?
Can we meet …?
Can we meet tomorrow?
Are you free/available…?
Are you free on Saturday?
I would like to book an appointment for…
I would like to book an appointment for next Thursday if it is possible.
If you want to cancel an appointment:
I’m afraid I wont’t be able to make it.
I’m afraid I have to cancel our appointment.
Unfortunately, I will be unable to keep our appointment.
Would it be possible/Is it possible to rebook our appointment for…?