Send Google Calendar appointment reminder SMS with RCSZilla

Description Send free SMS appointment reminders from Google Calendar with n8n and RCSZilla. This workflow turns Google Calendar into a simple appointment reminder system for opted-in customers. n8n checks tomorrow's events, reads the customer phone number and SMS consent from the calendar event description, prepares a short reminder message, and queues the SMS through RCSZilla. RCSZilla lets you use your own Android phone and SIM card as the SMS gateway, so you do not need a separate SMS API subscription just to send basic appointment reminders. The workflow is free to run in n8n, and RCSZilla supports device-based sending through your own mobile network. Your mobile carrier plan, country, and message volume can still affect real-world SMS costs, so check your plan before sending production traffic. Why This Workflow Is Useful Many appointment-based businesses need a practical SMS reminder service, but do not want to start with a paid SMS provider such as Twilio just to reduce no-shows. This template gives you a direct, phone-based setup: - Google Calendar stores the appointment. - n8n handles the automation logic. - RCSZilla queues the SMS. - Your connected Android device sends the message through its SIM/mobile plan. This is a good fit for salons, clinics, dentists, consultants, repair shops, real estate viewings, local agencies, auto service businesses, and other teams that already manage bookings in Google Calendar. How It Works 1. Daily Schedule The workflow runs once per day at 09:00. You can change the Schedule Trigger if your business sends reminders earlier, later, or on the same day as the appointment. 2. Google Calendar Lookup The Google Calendar node fetches tomorrow's events from the selected calendar. It only requests the fields needed for the reminder: event ID, title, description, start/end time, and location. 3. Appointment Data Parsing The Code node reads the event title, description, and location. It looks for: - Phone: or a phone-like number - SMS consent: yes - optional customer name - optional location If the event has no phone number, no positive SMS consent, or an opt-out phrase, the workflow does not send a message. 4. Consent Gate The IF node separates eligible reminders from skipped events. This makes the workflow safer to test because events without consent are routed away from the sending step. 5. SMS Queue With RCSZilla Eligible reminders are sent to the RCSZilla node using the SMS channel. RCSZilla then queues the message for the connected device that acts as your SMS/RCS gateway. 6. Skipped Reminder Summary Skipped events go to a summary node so you can inspect why a reminder was not sent. During setup, this helps you fix calendar descriptions before activating the workflow. RCSZilla Features Used Here This template uses RCSZilla as a phone-based messaging gateway for n8n: - Android device sending: connect your own Android phone and SIM card. - API access: generate an API key in RCSZilla and use it from n8n. - SMS channel: queue appointment reminders through the RCSZilla node. - Device-first setup: send through your own mobile network instead of starting with a paid SMS API provider. - Optional cloud sending: RCSZilla also documents optional credit-based cloud provider routing for users who do not want to send from a phone. RCSZilla setup guide: https://docs.rcszilla.com/?page=getstarted Requirements - n8n Cloud or self-hosted n8n. - RCSZilla account and API token. - Android device connected to RCSZilla and able to send SMS messages. - Active SIM/mobile plan for the device that will act as the SMS gateway. - Community node package: n8n-nodes-rcszilla. - Google Calendar OAuth credential in n8n. - Google Calendar events that include a customer phone number and SMS consent in the description. Setup Instructions 1. Install the RCSZilla community node in n8n: n8n-nodes-rcszilla. 2. Import the workflow JSON: Google Calendar appointment reminder SMS n8n - RCSZilla.json. 3. Create and assign the Google