WhatsApp Business API for inactive customer reactivation
The scenario sends a personalised WhatsApp marketing template to an existing customer who bought or used the service before but has been inactive for months.
Use case overview
The scenario sends a personalised WhatsApp marketing template to an existing customer who bought or used the service before but has been inactive for months. The message includes their name, the last product they purchased, the date of their last order or visit, and a tailored win-back incentive. A static URL button opens the store or account page to shop again.
Template example
Hello {{1}}! We miss you — your last order was on {{3}} for {{2}}. {{4}} Tap the button below to come back and shop with us again.
- {{1}}customer name
- {{2}}last purchased product name
- {{3}}date of last order or visit
- {{4}}win-back incentive or offer details
- “Shop again”button — fixed in the Meta template

When to use it
Use this scenario when you already have paying or active customers who have gone quiet for months — no recent order, visit, or login — and you want to win them back before they churn for good. It fits e-commerce recency segments built on purchase history, SaaS teams re-engaging users who stopped logging in after prior usage, and agencies running lapsed-customer win-back for client brands. It is not for dormant leads who never converted, nor for cross-sell right after a fresh purchase.
Workflow
- Trigger
CRM or ecommerce platform flags a recency segment of lapsed customers beyond the inactivity threshold.
event·triggered - Capture event
The system resolves phone numbers and last-purchase context for each contact in the segment.
phone:"+…" - Build & send
A personalised win-back template is built with four body variables and a static URL button.
POST/sendTemplate - Delivered
Each opted-in lapsed customer receives the WhatsApp reactivation message.
delivered - Status tracked
Delivery results are logged for churn-prevention campaign tracking and 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_PRODUCTNAME="___" # {{2}} product name
TEST_DATE="___" # {{3}} date or time
TEST_ADDITIONALINFO="___" # {{4}} additional info
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=$TEST_CUSTOMERNAME" \
"TEST_PRODUCTNAME=$TEST_PRODUCTNAME" \
"TEST_DATE=$TEST_DATE" \
"TEST_ADDITIONALINFO=$TEST_ADDITIONALINFO"; 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}} product name → ${TEST_PRODUCTNAME}
# {{3}} date or time → ${TEST_DATE}
# {{4}} additional info → ${TEST_ADDITIONALINFO}
read -r -d '' PAYLOAD <<JSON || true
{
"phone": "${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": "${TEST_PRODUCTNAME}" },
{ "type": "text", "text": "${TEST_DATE}" },
{ "type": "text", "text": "${TEST_ADDITIONALINFO}" }
]
}
]
}
JSON
RESPONSE="$(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. |

