Templates
Separate template types are used for appointments with and without a service line; content is filled based on the customer's language and the appointment details.
Which messages are sent?
From Settings → Messages & Notifications you can turn confirmation, reminder, cancellation, reschedule, and thank-you messages on/off individually and set the reminder lead time.
Quota
The monthly WhatsApp message limit depends on the plan (Free 50, Premium 500, Elite 1,500, Ultra 5,000). You can track usage in Communication analytics.