We added a new setting within the option asking clients to call to cancel their appointments. By default, clients are asked to call to cancel at all times. Now, you have the option to specify a period of time prior to the appointment during which cancellation is no longer allowed (24, 48, 72 hours).
For example if you specify 24 hours, your clients will be able to cancel their appointments online up to 24 hours before their appointment. After that, we will ask them to call. This could be configured to match your cancellation policy.
The following article explains how to do so: https://gorendezvoushelp.helpscoutdocs.com/article/232-can-i-make-clients-have-to-call-to-cancel-their-appointments-if-they-are-in-the-next-24-48-72-hours