WhatsApp appointment reminders for tomorrow's bookings

Every weekday at 8am, remind tomorrow's customers about their appointment over WhatsApp so I stop losing revenue to no-shows. Use a cron trigger scheduled Monday to Friday at 8am in my local timezone.

Start with Google Calendar List Events to pull every event on my bookings calendar for tomorrow. Expand recurring events into individual instances and order them by start time, so each real appointment is handled exactly once.

Then work through the events one at a time and decide which are genuine customer bookings. For each one, find the customer's mobile number, which may be written into the event description alongside the booking notes, or attached to a guest on the invite. Skip an event and record the reason when it is an internal meeting (team syncs, blocked-out or personal time, no external guest), when it has been cancelled, or when no mobile number can be found. Never guess or invent a number.

Important nuance to bake in: this reminder goes out roughly a day ahead, which makes it a business-initiated message sent well outside WhatsApp's 24 hour customer service window. It must therefore be sent with WhatsApp Send Message as a pre-approved template message rather than as free-form text, otherwise it will not be delivered. Use WhatsApp List Message Templates first to confirm my appointment reminder template is approved and to read the order of its variables, then pass the customer name, appointment time and location through as template variables in that order. Format every recipient number in full international format with no plus sign, spaces or dashes.

If a send fails, for example because the number is not on WhatsApp or the template variables do not match the approved template, do not stop the run. Record the failure against that customer and carry on with the remaining appointments.

Finish by posting a short recap to Slack with Slack Bot Send a Message. List who was reminded along with their appointment time, then list every booking that was skipped or failed with the reason for each, so I can chase anything that needs a manual phone call.