The rule in one paragraph
WhatsApp does not let businesses message anyone at any time. On the WhatsApp Business Platform (the Cloud API that Crosvia uses), a business can send free-form messages to a person only during the 24 hours after that person's most recent message. Meta calls this the customer service window.
Outside it, the only thing a business can send is a template message that Meta has reviewed and approved, and templates are billed. Every reply from the customer restarts the 24-hour clock.
That single rule shapes how a lead team should write, when it should call, and which automations are worth building. The details below come from Meta's WhatsApp Business Platform documentation and its Business Messaging Policy as published in 2026; Meta revises pricing and limits a few times a year, so check the live pages before budgeting.
Two kinds of message
Inside the window you can send session messages: plain text, images, PDFs, location pins, reply buttons, list menus, and anything else the API supports, with no prior approval.
Outside the window you can only send template messages. A template is a pre-written message with optional variables, submitted to Meta under one of three categories.
- Marketing: promotions, offers, new course launches. Highest cost, strictest review, and the person can opt out.
- Utility: messages tied to an existing request or transaction, such as "Your counselling session is confirmed for Tuesday 4 pm" or "Here is the fee receipt you asked for."
- Authentication: one-time passcodes.
Meta's review checks that the template fits its category and does not mislead. A counselling reminder submitted as marketing gets rejected; the same text submitted as utility is approved.
What it costs
Meta changed WhatsApp pricing in 2025 from per-conversation to per-template-message for marketing, utility and authentication templates, with service conversations (started by the customer) free. Rates differ by country; India has its own rate card. The working consequence for an Indian lead team is:
- A customer who messages you first costs nothing to reply to for 24 hours.
- A lead you message first costs one template send.
- Every re-engagement after silence costs another template send.
So the cheapest pipeline is the one where the customer does most of the opening. That is why the first template after a Meta lead form matters so much: it should earn a reply, because the reply opens a free window.
A worked example: one lead, seven days
Day 1: one template out, one reply in
7:42 pm. Priya submits a Meta lead form for a UK master's programme. No WhatsApp window exists yet, because she messaged the form, not your number.
Crosvia's automation sends a utility template: "Hi Priya, this is Anju from Horizon Overseas. You asked about UK master's intakes for September. Would you like the fee and scholarship sheet, or a quick call tomorrow?" Cost: one template.
7:55 pm. Priya replies "fee sheet please". The 24-hour window opens. Anju sends the PDF and two follow-up questions as free session messages. Cost: nothing.
Day 2: the call, still inside the free window
10:10 am. Anju calls from the call queue, speaks for nine minutes, and logs the disposition as interested, follow-up Friday.
The window is still open — it closes at 7:55 pm on day 2 — so she sends a free summary message with the three shortlisted universities.
Day 5: one more template to re-open the window
Priya has not messaged since day 1, and the window closed on day 2. The scheduled follow-up fires a utility template referencing the shortlist. Cost: one template.
Priya replies with a question about IELTS. A new window opens, and the rest of the conversation that day is free.
The week in totals
Over seven days the brand sent two templates and roughly twenty free messages. Had the counsellor tried to send the day-5 follow-up as a plain message, the API would have rejected it with a 131047 error (re-engagement message outside window) and the lead would have heard nothing.
What this means for how you write
Because a reply restarts the clock, every message inside the window should end with something easy to answer. "Shall I send the fee sheet or the scholarship list first?" keeps a conversation alive. "Let me know if you have any questions" usually ends it.
Because templates are reviewed, write them once and write them well. Utility templates that reference the person's actual request (programme, city, treatment, property) are approved faster and read as service rather than spam. Keep a short library: first contact after a lead form, appointment confirmation, appointment reminder, document request, payment link, and a polite re-engagement.
Because marketing templates have opt-outs and higher cost, do not use them for one-to-one follow-ups. Save them for genuine announcements to people who have consented to hear them.
What this means for automation
- First contact after a lead form must be a template. Build it as an automation on lead created with source Meta Lead Ads.
- Follow-up reminders should check the window. If the window is open, send a session message; if closed, send the utility template. Crosvia does this check before every outbound message and shows the window state at the top of the thread.
- Do not schedule messages for a time the window will have closed unless they are templates.
- The 24-hour window also governs the AI teammate: it can reply freely inside the window and proposes a template when the window is closed.
Consent sits on top of all this
The window is a WhatsApp rule. India's Digital Personal Data Protection Act 2023 adds a separate requirement: you need a lawful basis, normally consent, to process a person's phone number for messaging.
A lead form where the person asks to be contacted is a reasonable basis for the first message about that enquiry; it is not consent for unrelated marketing. Crosvia records consent per channel on the lead so that the template library and the broadcast tools respect it.
What to do next
- Connect your number through Embedded Signup: WhatsApp Cloud API integration.
- See the window state and template picker in the shared inbox: Inbox.
- Automate the first template and the window-aware follow-up: Automations.
- Related terms: 24-hour window, WhatsApp template message, consent.
- How speed in that first hour changes outcomes: Speed to lead on Meta ads.