Email and SMS notifications for key booking events Use WhatsApp as the main communication channel, complemented by email for important booking events: New booking confirmation → WhatsApp + Email Rescheduling confirmation → WhatsApp + Email Cancellation confirmation → WhatsApp + Email Reminders, preparation instructions and confirmation requests → WhatsApp only SMS fallback In the rare case where the client does not have WhatsApp, it would be useful to have SMS as a fallback channel for reminders, even if this involves an additional cost. Ideally, the SMS reminder should include the same confirmation/cancellation links or buttons used in the WhatsApp flow, so the client can respond and trigger the same double-confirmation workflow and update the appointment status in the system.