If you want to prevent your attendees from cancelling or rescheduling a meeting, begin by opening the Pages dashboard. Click on the meeting type that you want to edit.
From here, select Scheduling Rules and scroll to the bottom of the page. You can use the toggle switch to allow or not allow cancellations and rescheduling. When in the off position, your attendees will lose this option but your meeting hosts will still be able to cancel or reschedule as needed.