WhatsApp Business API for offline payment notification

Use case overview

The scenario sends the customer a personalised WhatsApp template when an offline payment is recorded. The message includes the customer name, payment amount, and payment date. A static URL button opens the receipt or payment history page.

Template example

Hello, {{1}}! We recorded your offline payment of {{2}} on {{3}}. Thank you.

[View receipt]

The receipt URL button is fixed in the Meta template — only body variables are sent via the API.

Variables and purpose

• {{1}} — customer name
• {{2}} — payment amount
• {{3}} — payment date

Filled-in example

Hello, Alex! We recorded your offline payment of 500.00 USD on June 28, 2026. Thank you.

[View receipt]

When to use it

• retail and field service
• bank transfers
• integrators

Business value

• Staff or billing system records an offline payment against the customer account
• System captures the payment event and resolves the customer phone number
• Personalised template message is prepared with customer name, amount, and payment date
• WhatsApp template notification is delivered to the customer
• Customer can open the receipt via the static URL button; delivery status is logged

Workflow

1. Staff or billing records an offline payment and fires a confirmation event.
2. The system resolves the customer phone number and payment fields.
3. A personalised template message is built with three body variables and a static URL button.
4. The customer receives the WhatsApp notification and can open the receipt via the button.
5. Delivery result is logged for billing or CRM follow-up.
6. Delivery progress is reported asynchronously — typically sent, then delivered (or failed/undelivered).
7. Your system receives status via webhook (hooks[]) or polls GET …/hookInfo?messageId=<id> and handles failures if needed.

Technical implementation

Prerequisites

• A 1MSG account with WhatsApp Business API connected and an approved message template.
• Customer phone number in international format (without + and spaces).
• Payment data: customer name, amount, payment date.

Code examples

#!/usr/bin/env node

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

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

const TEMPLATE_NAME = "___";                // approved template name
const TEMPLATE_NAMESPACE = "___";           // template namespace (422 without it)
const TEMPLATE_LANGUAGE = "___";            // template language code, e.g. "en"



// === Test data ===
const TEST_PHONE = "___";            // client phone in international format
const TEST_CUSTOMERNAME = "___";    // {{1}} customer name
const TEST_PAYMENTAMOUNT = "___";    // {{2}} payment amount
const TEST_DATE = "___";    // {{3}} date or time

function normalizePhone(phone) {
  return String(phone).replace(/\D/g, "");
}

function assertConfigured(values) {
  for (const [key, value] of Object.entries(values)) {
    if (value === "___" || value === "" || value === undefined || value === null) {
      throw new Error(`Missing configuration value: ${key}`);
    }
  }
}

async function sendTemplateMessage({ phone, customerName, paymentAmount, date }) {
  assertConfigured({
    CHANNEL_ID,
    API_TOKEN,
    TEMPLATE_NAME,
    TEMPLATE_NAMESPACE,
    TEMPLATE_LANGUAGE,
    phone,
    customerName,
    paymentAmount,
    date,
  });

  const url = `${API_BASE_URL}/${CHANNEL_ID}/sendTemplate`;

  // params carries body ONLY. Button text is fixed in the Meta template — no button param.
  const requestBody = {
    phone: normalizePhone(phone),
    template: TEMPLATE_NAME,
    namespace: TEMPLATE_NAMESPACE,
    language: {
      policy: "deterministic",
      code: TEMPLATE_LANGUAGE,
    },
    params: [
      {
        type: "body",
        parameters: [
          { type: "text", text: String(customerName) }, // {{1}} customer name
          { type: "text", text: String(paymentAmount) }, // {{2}} payment amount
          { type: "text", text: String(date) }, // {{3}} date or time
        ],
      },
    ],
  };

  const res = await fetch(url, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${API_TOKEN}`,
    },
    body: JSON.stringify(requestBody),
  });

  const raw = await res.text();
  let data;
  try {
    data = JSON.parse(raw);
  } catch {
    data = null;
  }

  if (!res.ok || !data || data.sent !== true) {
    console.error("Send failed. API response:");
    console.error(raw);
    process.exit(1);
  }

  console.log("Message sent to client.");
  console.log("API response:", raw);
  return data;
}

if (require.main === module) {
  sendTemplateMessage({
    phone: TEST_PHONE,
    customerName: TEST_CUSTOMERNAME,
    paymentAmount: TEST_PAYMENTAMOUNT,
    date: TEST_DATE,
  }).catch((err) => {
    console.error("Execution failed:", err.message);
    process.exit(1);
  });
}

module.exports = { sendTemplateMessage };

Immediate API response (synchronous)

• 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 from the response (value looks like wamid.…). Use it to correlate delivery callbacks or polling.
• The response may also include message and description — informational only.

Delivery status (asynchronous)

• Register a webhook (POST …/webhook) so 1MSG POSTs delivery updates to your HTTPS endpoint in a separate `hooks[]` payload (sent, delivered, read, or failed/undelivered when applicable).
• Optionally poll: GET {base}/{channel}/hookInfo?messageId=<id from sendTemplate>.
• In practice, delivery often completes within a few seconds — but that is not guaranteed by the API contract.

Common errors

• Invalid or non-normalized phone number
• Unapproved or missing template name / namespace
• No customer opt-in for WhatsApp business messages
• Template variable count mismatch (422 from API)
• Delivery failure — check status webhook and retry policy

FAQ

• Do I need an approved template? Yes — cold-start WhatsApp messages require a Meta-approved template.
• Can I customize the message text? Body variables are dynamic; fixed text and button labels are set in the Meta template.
• How do I check delivery? sent: true only confirms acceptance. Track delivery via webhook hooks[] or GET …/hookInfo?messageId=<id>.
• What if the message is not delivered? Log the failed/undelivered hook, verify opt-in and template status, then retry or fall back to another channel.
• Can I connect this to my CRM or backend? Yes — trigger the API call from your platform webhook or event handler.

Related

• Knowledge base
• Creating a template
• Sending a template
• SDK