If you are an admin
To reschedule an appointment like this, first assign the patient to the new doctor within their case file. Once this is done, cancel the appointment in the booking calendar and give a reason. Explain in this box that they will receive new details by email shortly. Also be sure to tell them to ignore recent recent invoices and that a new one will be issued shortly. (The patient will be notified and can see the reason.) Now go to Invoices, find the pending invoice and click Mark Cancelled.
Then create the new appointment with the new psychiatrist (Provisional). When the box appears asking for payment, choose Pay Later. This will then set the new appointment and when the patient has paid for the appointment, an email will be sent to the new psychiatrist asking them to approve the appointment. The patient will get an email with the invoice of £0.00 (Paid). When the new psychiatrist approves the appointment, the patient will get confirmation of the new appointment with links for that appointment (as will the psychiatrist).
Once the appointment has been confirmed, the patient will receive confirmation of the new appointment with links for that appointment (as will the psychiatrist).