You need to make sure that you have created a new available schedule of the time you are moving the appointment to, for example in this case, we have added a schedule for March 12 at 11:00AM:
2. From the booking, click on the "move all bookings" button to update the time and date of the appointment (if you want to move all bookings from one time to another booking date and time)
***If you want to move one booking to a different time, kindly follow the steps on the link below:
http://help.flexbooker.com/getting-started/how-to-update-a-booking-time-and-date-for-an-individual-customer-using-a-fixed-time-schedule
3. The system would then allow you to choose on an available time from the calendar:
4. When you have chosen a time and date, the system would show the message that you have successfully moved the customers to this updated time and date: