State the cutoff plainly
Say how many hours before the appointment cancellations are free.
Explain the fee
Say what it costs to cancel late and why the policy exists.
Show how to cancel
Give the link or number to use, and what counts as cancelled.
Handle a past-the-window request
Be kind and say what you can offer, such as a reschedule.
Allow clear exceptions
Mention emergencies and how you decide on them.
Put it in the booking message
Include the window in confirmations so it is not a surprise.