WhatsApp Business API for booking change notification
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}}.
- {{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

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.
Workflow
- Trigger
The scheduling system detects a booking change and fires an event.
event·triggered - Capture event
The system resolves the client phone number and updated fields.
phone:"+…" - Build & send
A personalised template message is built with four body variables and a static URL button.
POST/sendTemplate - Delivered
The client receives the WhatsApp notification with updated details.
delivered - Status tracked
Delivery result is logged for scheduling or CRM follow-up.
status:"read"

Technical implementation
Prerequisites
- 1MSG API Key · How to get API Key
- WhatsApp Business account · How to Connect WABA
- WhatsApp Template · How to Approve WABA Template
- 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.
{
"sent": true,
"id": "wamid.HBgLMzgwNjM5...",
"message": "Message accepted for delivery"
}sentAccepted for sending — not yet on the customer's phone
idStore it; delivery callbacks and
hookInfoare keyed on this
Delivery itself arrives later, as a separate callback. Register a webhook (POST …/webhook) and 1MSG POSTs status updates to your HTTPS endpoint in a top-level hooks[] payload.
{
"hooks": [
{
"id": "gBGGeSaGViBfAgnlzOSHEwK9O6F",
"type": "message",
"status": "sent",
"timestamp": "1654864094",
"recipient_id": "556123122026"
}
]
}statussent,delivered,read— or a failure status when applicableidCorrelates the callback with the
idreturned by the send calltimestampUnix seconds, as a string
If you would rather not receive callbacks, poll GET {base}/{channel}/hookInfo?messageId=<id> instead. In practice delivery often completes within seconds — but the API contract does not guarantee it, so never block a flow waiting on it.
Common errors
| Status | Response | Cause |
|---|---|---|
| 200 | Message was not sent: template is not defined | namespace, template or language missing from the request body. |
| 200 | template name (…) does not exist in <language> | The template is approved in a different language than the one requested. |
| 200 | Message was not sent: provide chatId, phone, bsuid, or username | No recipient the channel could resolve. |
| 403 | access denied | The token is wrong, or belongs to a different channel than the URL. |
| 429 | too many requests. please try later | The channel is over its send rate. |

