You can always cancel an appointment and issue a refund if a payment has already been initiated. You can also delete a client from your business too.
To issue a refund for a specific appoinment, Click on the transaction-in-question within the Billing section of your Fons account. The appointment details page will present you with an "issue refund" button. Click that and you’re good to go!
To issue a refund for a payment request, navigate to the Billing tab and under Payment Requests you will be able to offer refunds for requests that have been paid for.