The 24-hour customer service window

WhatsApp lets you send any message for 24 hours after a customer last wrote to you. After that, only an approved template can reach them. When the window has closed, Zymbler replaces the reply box with a Choose a template button, or a link to Templates if you have no approved ones yet. Pick a template and send it. Meta's rules here are as of October 2026.

What the window is

When a customer messages you or calls you, Meta starts a 24-hour timer called the customer service window. If they message or call again before it runs out, the timer resets to 24 hours.

• Inside the window Meta allows any service message: text, images, documents and more, with no pre-approval. Zymbler's reply box sends text.
• Outside the window only pre-approved template messages can be sent.

If a message fails because the window has closed, Meta returns error 131047, often shown as “Re-engagement message”. Meta's description is “More than 24 hours have passed since the recipient last replied to the sender number.” Its fix is to send a template message instead.

What Zymbler shows

• A countdown in the chat header, such as “18h left” or “42m left”. It turns amber under 6 hours and red under 1 hour. Hover over it to see “Free-form replies are allowed until this runs out”.
• “Window closed” once the 24 hours are up. The reply box is replaced by “The 24-hour window has closed. Only an approved template will reach Maya now.” (with your customer's name) and, if you have approved templates, a Choose a template button.
• A “Not delivered” bubble if a reply you typed goes out just as the window closes: “Not delivered. More than 24 hours since they last wrote. Send a template instead.” This is Meta's error 131047.

How the agent and workflows fit in

The agent only replies to messages the customer has just sent, so it always works inside the window. Anything Zymbler starts on its own, such as a workflow or the first message to a Facebook lead, is sent as an approved template.

The Let the AI pick the conversation back up setting (Settings, under WhatsApp) is for replies your team sends from the WhatsApp Business app. Once your side has been quiet for 1 to 24 hours, the agent answers the customer's next message. A chat a teammate took over in Zymbler stays with them until they hand it back. The limit is 24 hours because that is when the window closes.

What it costs since 1 October 2026

Meta bills these messages to your own WhatsApp Business account, not through Zymbler.

• Service messages (your replies inside the window) are charged per message after the first 1,000 free ones each month for each business phone number.
• Utility templates sent as a reply inside the window are charged too, from the first one: the 1,000 free messages cover service messages only. They had been free since 1 July 2025.
• If a customer taps a Click-to-WhatsApp ad in the WhatsApp phone app (Android or iPhone) and you reply within 24 hours, Meta opens a free entry point window. Meta doesn't charge for marketing, utility, authentication or service messages in it. Meta's developer page says it can stay open up to 7 days; the WhatsApp Business website says 72 hours. Plan on 72 hours.

Work out your own numbers in the pricing calculator or read the pricing change guide.