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Booking change notification via WhatsApp API

The scenario sends the client a personalised WhatsApp template when booking details change.

Use case overview

The scenario sends the client a personalised WhatsApp template when booking details change. The message includes the client name, service name, summary of changes, and updated date. A static URL button opens booking details.

Template example

Hello, {{1}}! Your booking for {{2}} has changed: {{3}}. New date: {{4}}.

View booking
  • {{1}}
    customer name
  • {{2}}
    service or reservation type
  • {{3}}
    summary of what changed
  • {{4}}
    updated booking date
  • “View booking”
    button — fixed in the Meta template
WhatsApp Business API for booking change notification

When to use it

Use this scenario when a confirmed appointment or reservation changes in the scheduling system and the client needs to know before they arrive at the wrong time. It fits scheduling platforms, clinics and salons that adjust time or service, and integrators piping calendar or CRM change events into WhatsApp outbound.

Fewer "what changed?" support calls
Four body variables carry the client name, service, a plain summary of what changed, and the new date, so the update lands in WhatsApp with every detail they would otherwise call to confirm.
Fewer missed appointments after a reschedule
The change summary and updated date replace the old slot in the client's chat, and the static View booking button opens the full reservation for anything the message does not cover.
No manual re-notification work
The scheduling system fires the template on the booking-change event, resolves the phone number, and sends — no rep retypes the new time for each affected client.
Reach clients with no open chat
An approved template can go out proactively when there is no active WhatsApp session, so the update does not wait for the client to message first.
Delivery logged back to scheduling or CRM
Send result is recorded for follow-up in the scheduling system or CRM, so the team knows whether the client received the new details.

Workflow

  1. Trigger

    The scheduling system detects a booking change and fires an event.

    event · triggered

  2. Capture event

    The system resolves the client phone number and updated fields.

    phone: "+…"

  3. Build & send

    A personalised template message is built with four body variables and a static URL button.

    POST /sendTemplate

  4. Delivered

    The client receives the WhatsApp notification with updated details.

    delivered

  5. Status tracked

    Delivery result is logged for scheduling or CRM follow-up.

    status: "read"

WhatsApp Business API for booking change notification

Technical implementation

Prerequisites

  1. 1MSG API Key · How to get API Key
  2. WhatsApp Business account · How to Connect WABA
  3. WhatsApp Template · How to Approve WABA Template
  4. Customer opt-in · How to Manage Customers Consent

Code examples

#!/usr/bin/env bash
set -euo pipefail

# === Configuration (replace "___" placeholders) ===

API_BASE_URL="https://api.1msg.io"        # production 1MSG API base URL
CHANNEL_ID="___"                           # channel ID from 1MSG dashboard
API_TOKEN="___"                            # channel JWT token (Bearer)

TEMPLATE_NAME="___"                        # approved template name
TEMPLATE_NAMESPACE="___"                   # template namespace (required — send fails without it)
TEMPLATE_LANGUAGE="___"                    # template language code, e.g. "en"



# === Test data ===
TEST_PHONE="___"                 # client phone in international format
TEST_CUSTOMERNAME="___"         # {{1}} customer name
TEST_SERVICE="___"         # {{2}} service name
TEST_DETAILS="___"         # {{3}} change details
TEST_BOOKINGDATE="___"         # {{4}} booking date

PHONE_NORM="$(printf '%s' "$TEST_PHONE" | tr -cd '0-9')"

for pair in "CHANNEL_ID=$CHANNEL_ID" "API_TOKEN=$API_TOKEN" \
            "TEMPLATE_NAME=$TEMPLATE_NAME" "TEMPLATE_NAMESPACE=$TEMPLATE_NAMESPACE" \
            "TEMPLATE_LANGUAGE=$TEMPLATE_LANGUAGE" "TEST_PHONE=$TEST_PHONE" \
            "TEST_CUSTOMERNAME=$TEST_CUSTOMERNAME" \
            "TEST_SERVICE=$TEST_SERVICE" \
            "TEST_DETAILS=$TEST_DETAILS" \
            "TEST_BOOKINGDATE=$TEST_BOOKINGDATE"; do
    val="${pair#*=}"
    if [ -z "$val" ] || [ "$val" = "___" ]; then
        echo "Missing configuration value: ${pair%%=*}" >&2
        exit 1
    fi
done

if [ -z "$PHONE_NORM" ]; then
    echo "Error: phone number has no digits after normalization" >&2
    exit 1
fi

URL="${API_BASE_URL%/}/${CHANNEL_ID}/sendTemplate"

# params carries body ONLY. Button text is fixed in the Meta template — no button param.

# {{1}} customer name → ${TEST_CUSTOMERNAME}
# {{2}} service name → ${TEST_SERVICE}
# {{3}} change details → ${TEST_DETAILS}
# {{4}} booking date → ${TEST_BOOKINGDATE}
read -r -d '' PAYLOAD <<JSON || true
{
  "phone": "${PHONE_NORM}",
  "template": "${TEMPLATE_NAME}",
  "namespace": "${TEMPLATE_NAMESPACE}",
  "language": { "policy": "deterministic", "code": "${TEMPLATE_LANGUAGE}" },
  "params": [
    {
      "type": "body",
      "parameters": [
        { "type": "text", "text": "${TEST_CUSTOMERNAME}" },
        { "type": "text", "text": "${TEST_SERVICE}" },
        { "type": "text", "text": "${TEST_DETAILS}" },
        { "type": "text", "text": "${TEST_BOOKINGDATE}" }
      ]
    }

  ]
}
JSON

RESPONSE="$(curl -s -w '\n%{http_code}' -X POST "$URL" \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer ${API_TOKEN}" \
    -d "$PAYLOAD")"

HTTP_CODE="$(printf '%s' "$RESPONSE" | tail -n1)"
BODY="$(printf '%s' "$RESPONSE" | sed '$d')"

case "$BODY" in
    *'"sent":true'*) ok=1 ;;
    *) ok=0 ;;
esac

if [ "$HTTP_CODE" -ge 200 ] && [ "$HTTP_CODE" -lt 300 ] && [ "$ok" -eq 1 ]; then
    echo "Message sent to client."
    echo "API response: $BODY"
else
    echo "Send failed. HTTP status: $HTTP_CODE" >&2
    echo "$BODY" >&2
    exit 1
fi

Response and delivery status

HTTP 2xx and JSON "sent": true mean 1MSG accepted the message for sending — not that it already reached the customer's phone. Save the id field (looks like wamid.…) to correlate delivery callbacks.

200 OKResponse
{
  "sent": true,
  "message": "Sent to [email protected]",
  "description": "Message has been sent to the provider",
  "id": "wamid.HBgLMzgwNjM5..."
}
  • sent

    Accepted for sending — not yet on the customer's phone

  • id

    Store it; delivery callbacks and hookInfo are keyed on this

Delivery statuses and webhooks →

Common errors

StatusAPI responseCauseFix
200Message was not sent: template is not definednamespace, template or language is missing from the request body.Send all three. Take namespace and the exact template name from GET /templates; language is an object: {"policy": "deterministic", "code": "en"}.
200template name (…) does not exist in <language>The template is approved in a different language than the one requested.Use the exact language code the template was approved in (for example es_MX is not the same as es). Check it in GET /templates.
200Message was not sent: provide chatId, phone, bsuid, or usernameNo recipient the channel could resolve.Pass exactly one recipient: phone (country code plus number, digits only), chatId (for example [email protected]) or bsuid.

All error codes →

Common questions

Related

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