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WhatsApp charges per message. Every template you send is its own charge, at a rate that depends on the recipient’s country and the kind of message. The 24-hour window is a separate thing, and the two are easy to confuse: the window decides what you are allowed to send, not how a charge is counted.

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The 24-hour customer service window

When a customer messages you, a 24-hour window opens. Inside it, the agent replies freely, in its own words, as many times as the conversation needs. Cards, buttons, images — anything. Outside it, nothing but an approved template reaches that customer. Not a short message, not a follow-up question. Nothing.
Every customer message resets the window to a fresh 24 hours. A conversation that goes back and forth over three days never leaves the window.

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What gets charged

Messages your customers send you are never charged.
An open window makes two things free, not one. Until 1 October 2026 it covers the agent’s own replies and any utility template you send while the window is open. So an order update sent to somebody who is mid-conversation with you costs nothing, where the same template sent a day later is charged.Authentication is the exception: a one-time passcode is charged whether or not a window is open.
This is why answering is cheap and starting is expensive. An agent handling forty inbound questions costs a fraction of forty marketing sends. Support automation pays for itself long before outbound does.
Rates vary by country and change from time to time — India differs from the US by a large multiple. Your usage page itemises what you were actually charged, by category and country.

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Who bills you, and for what

Two things are being paid for and they arrive from different places, which is the single most common question about a WhatsApp bill. Meta charges for the message. The rates above are Meta’s, they vary by country, and they are the bulk of the cost. ThinnestAI charges 10% of Meta’s rate, per message — the platform fee. It pays for the console, the shared inbox, templates, forms, delivery reporting and keeping your conversations. Which of us Meta invoices depends on whose WhatsApp Business Account the message went out on. Either way our share is the same 10% of the same rate. On your own account you will see two charges for one message — Meta’s on your Meta bill, ours on your usage page — and that is expected rather than a duplicate.
Money added in one place does not cover the other. A balance topped up here cannot pay Meta’s message fees, and a payment method added on Meta does not pay our platform fee. If sending stops, check which of the two is empty: a Meta payment problem stops messages being delivered at all and says so on your WhatsApp page, where an empty balance here stops campaigns before they start.
Your agent’s own replies are charged separately from messages — what the model costs us, plus the same 10% — and are itemised on your usage page. Calls are priced per minute. Neither has anything to do with Meta’s message rates.

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In-window messages become chargeable on 1 October 2026

This one is worth planning for. Two things that are free today stop being free on 1 October 2026:
  • The agent’s own free-form replies inside the 24-hour window, which is most of what it sends.
  • Utility templates sent while a window is open.
Both are then charged at the ordinary utility rate for that country. A WhatsApp conversation gets more expensive on that date, and if you run pay-as-you-go your balance will drain faster than it does now.
You will not have to remember this. A notice appears on your usage page in the run-up, and you get a notification before the date — so the first you hear of it is not a smaller balance than you expected. Nothing about how the agent works changes, and nothing you have built needs rebuilding. What changes is the arithmetic: today a long back-and-forth costs almost nothing, and after that date each of the agent’s replies carries a charge.

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The free entry point

72 hours free

When a customer arrives from a click-to-WhatsApp ad or a Facebook page call-to-action, and you reply within 24 hours, nothing in that conversation is charged — for 72 hours. Marketing templates included.
Three times the normal window, at no cost, and it covers the most expensive category on the rate card. If you run WhatsApp ads at all, this changes the economics of answering quickly: a reply inside 24 hours turns a paid conversation into a free one. Free entry point conversations show in your usage.

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What this means in practice

A reply within 24 hours of a click-to-WhatsApp ad buys 72 free hours. A reply on day two buys nothing.
Every template is charged. Two separate utility messages an hour apart cost twice what one message covering both would.
Until October 2026 an order update, a reminder or a receipt costs nothing if the customer is still inside their 24-hour window, and the ordinary rate the moment it closes. The same message, the same template, two different prices — so timing it with the conversation is worth real money on any volume.
Inside the window the agent can simply answer, in its own words, for nothing. Check the inbox before sending a template to somebody you are already talking to.
Far cheaper than marketing, and it reaches customers who opted out of marketing. Only where it genuinely is utility — see the categories.

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What you cannot do, at any price

  • Send free-form text outside the window. No amount of paying unlocks this.
  • Send marketing to somebody who opted out. Refused, and correctly.
  • Open a window by sending yourself a message. The window is opened by the customer, or by a template you pay for.