All appointments in Cliniko have a "paper trail" so that you can see which users have changed what (and when)! You can find that information by following these steps.
See an appointment's log of changes
Find the patient in question, and click on Appointments:
You'll see a log of all appointments (including cancelled ones) for this patient:
To view the "paper trail" of any appointment, click the View log button:
You'll see the all the details about anything relating to that appointment, from the moment it was created!
You can also see the log of changes to invoices and payments. Head on over here to check it out!