Missed call text back, and why we will never build it

A missed call text back sends a message to somebody who did not message you. That is the whole problem, and it is a technical description rather than a criticism: on WhatsApp the rules turn on whether the recipient wrote to you first, and a caller has not written to you at all. We do not build this, and the most useful thing on this page is that Meta’s own documentation is not unanimous about why.

The line every WhatsApp rule sits on

Meta divides messages by whether a window is open, not by how urgent you feel, and what that window permits and what closes it decides every question below. Its pricing page states the limit on free-form messages in one sentence: “Non-template messages can only be sent within an open customer service window.” The service messages page describes what those are, “Service messages are free-form messages that you can send to WhatsApp users during a customer service window”, and what happens at the boundary: “When the window closes, you can only send pre-approved template messages.”

A caller is on the far side of that boundary by construction: they rang, you missed it, and nothing they did was a message. So the question is whether a call opens a window, and here the sources stop agreeing.

Meta’s pages do not describe the trigger the same way

Four pages, read the same day, define what starts the 24-hour window:

Meta page	How it describes what opens the window
Service messages	“When a WhatsApp user messages you or calls you, a 24-hour timer called a customer service window starts.”
Pricing	“it still can only be sent in an open 24-hour customer service window which opens and resets with each user message”
Upcoming pricing updates	“Within the 24-hour customer service window, which opens and resets with each user message”
Messaging Policy	“You may reply to a user message without use of a Message Template as long as it’s within 24 hours of the last user message.”

One page says messages or calls. The other three say messages, twice in identical phrasing, and the policy attaches the 24 hours to “the last user message”. The service messages page is not slipping, either: it repeats the inclusion, saying service messages can be composed as needed “in response to a WhatsApp user’s message or call”.

Only Meta can resolve that. What we can say is which way it cuts. If the service messages page governs, a caller who reaches you on WhatsApp has opened a window, and your reply inside it is a free-form service message rather than a template, needing no approval. That partly complicates our own refusal, which is worth saying rather than hiding.

The call that opens a window is not the call you missed

Read the enabling conditions and the complication mostly dissolves. The Calling API page is explicit about which calls it means: “The Calling API supports receiving calls made by WhatsApp users to your business”, and it lists a prerequisite, “Enable Calling API features on your business phone number”.

So the window-opening call is a WhatsApp call, placed inside WhatsApp, to a business number configured to receive them. That is our reading of those two pages rather than a quotation. A caller who rings your ordinary phone line has generated no WhatsApp event at all, so there is nothing for a window to attach to, and texting them is reaching out.

Meta does record unanswered WhatsApp calls as events: its webhook reference says “Even unanswered calls are considered completed”, with no start_time, end_time or duration. What no page we read says is whether an unanswered call opens the window. The service messages page says calls open it and never distinguishes connected calls from missed ones, so anyone confident either way is not quoting Meta.

If it is a template, Meta has already named the closest case

Suppose no window. Then the text back is a template, with the approval step and the per-delivery charge that any outbound reminder carries, and Meta’s template categorization page has a utility objective that fits almost exactly: Continue a Conversation on WhatsApp, described as “Send a message to begin an interaction on WhatsApp that began in another channel.” A failed phone call is a conversation that began in another channel.

The same entry carries the condition automation cannot satisfy: “These messages should not be initiated without a user having requested the conversation to be moved to WhatsApp.” A missed call is not a request to move channel, and the point of the feature is that it fires without anybody asking.

Without that request, the nearest objective is on the marketing side of the page, where Meta describes building customer relationships as strengthening them “through personalized messages or by prompting new conversations”, and warns of retargeting that “These are marketing even if requested by users”. Marketing is the more expensive category.

Opt-in, and the one thing a missed call genuinely earns you

Category is not the gate anyway. Permission is. Meta’s opt-in page opens with the obligation, “Businesses are required to obtain opt-in before messaging people on WhatsApp”, and the service messages page repeats it as a limit on sends: “As a reminder, you can only send messages to WhatsApp users who have opted in to receiving messages from you.” Meta hands the legal test back, “It is up to businesses to determine the method of opt-in”, and the messaging policy adds a line that describes this feature’s failure mode well: “Do not confuse, deceive, defraud, mislead, spam, or surprise people with your communications.”

The constructive part is on the same page. Among the supported methods Meta lists “By phone (using an interactive voice response (IVR) flow)”. So the call you missed is a place to collect consent, and a greeting that offers to text is a legitimate opt-in step. That is the opposite design from texting everyone who rang, and once the caller writes first the reply is an ordinary one, free-form and answerable the next morning.

The SMS version is a different regime, and we are not summarising it

The SMS version of this feature is not governed by any of the pages above. It sits under telecoms regulation, which varies by country and by class of message, and we have not read a primary regulatory source to a standard we would publish, so we are not going to summarise telecoms rules here. Check the ones that apply where you operate, and treat a vendor page that explains neither regime as evidence about the vendor. We will not name one we have not fetched and cited, the same discipline applied to review management software.

What Meta documents for a missed call, instead of a text

For a missed WhatsApp call there is a sanctioned route, and it is not a message. The business-initiated calls page describes a setting: “When callback_permission_status is enabled, the user automatically provides call permission to your business when they place a call to you.” Calling somebody back who tried to call you is the behaviour Meta built a permission model for.

Cost is moving too. From Meta’s pricing page, “Meta will charge on a per-message basis for service messages”, effective October 1, 2026, so even the free-form reply inside an open window stops being free, with the allowance and the delivery stop that come with that date.

The actual answer

A missed call text back is outbound on WhatsApp unless the caller rang you inside WhatsApp, and Meta’s pages disagree about whether even that opens a window. On SMS it is somebody else’s rulebook. mesej never messages anyone first, so this is not a roadmap gap: nothing here turns a missed call into a message, because a send takes a target minted from a conversation the customer opened rather than a number you hand it, and no channel is connected to it anyway. The honest options for a missed call are a human, a callback, or a greeting that asks the caller to message you, and only the last one makes the conversation theirs to start. If the first of those is what you actually need, a telephone answering service answers the phone and this does not.