Hi [email protected] ,
Thank you for your inquire.

We have option 'Minimum time required before canceling/rescheduling" so you can set minutes, hours, days or weeks before the appointment and in that period customer will not be able to cancel or reschedule the appointment. In that case, they would need to contact you and request cancelation or rescheduling. However, you should know that we don't have 'Request a refund' option, once customer cancels the appointment your employee or you (depending how you set it) would receive notification about it and you would need to refund manually from PayPal or Stripe.

There is an option also for administrators to cancel the appointments and also you can include the cancellation link in the email notification so the customers can click on it and cancel as well.

You can check all of the plugin features on our demo sites 

https://wpamelia.com/demos/

Best regards.