At the bottom of your appointment windows, you'll notice a checkbox that reads "Notify client of change."
This feature allows you to prevent automated messages from being delivered in response to appointment changes you make.
Deselect the box to prevent any automated message from being sent regarding the appointment change.
When the box is checked, only messages turned ON in your Automated Messages section are sent regarding the appointment change.
Note: The "Notify client of change" box is only available on existing appointments. When scheduling a new appointment you will not see this box.