To turn off sending SMS notifications when creating an appointment in the appointment journal, go to the Settings - Notification types section and uncheck the box next to the Client notification of offline booking. If necessary, you can turn on the sending of this notification in the same section.
Despite the prohibition of sending this type of notification, SMS with details of the booking can still be sent individually.
To do this, when creating an appointment, go to the Notifications of the Appointment card and set up the sending: check the box next to Send SMS.
Also here you can change the time of sending a reminder to the client about the forthcoming appointment (more details in this article).