Missed call text back: what it is, the consent rules and the math

Missed call text back is an automatic text message your business number sends when a call goes unanswered. Within a minute or so the caller gets something like “Hi, this is Ruiz Plumbing, sorry we missed your call. What can we help you with?”, and the conversation continues by text while you finish the job you were on.

The idea is simple. The rules around it are not, because a text from a business to a cell phone falls under federal law, carrier registration and, in Texas, a state law that changed in 2025. This guide covers how it works, the consent rules, and how to tell whether it pays for your business without anyone making up a number for you.

How it works

1. A customer calls your business number and nobody picks up. You’re under a sink in Socorro, or it’s 7 p.m. and the shop is closed.
2. The phone system sees the missed call and sends one text from the same business number. It says who you are, says you missed the call, and asks what they need.
3. The reply lands in an inbox your team checks, on the computer or a phone app. Someone answers, books the job or calls back at a better time.

A few practical limits. Texts only reach phones that can receive them, so a call from an office landline usually gets nothing. The business number has to be set up and registered for texting first (more on that below). And someone has to answer the replies; an automatic first text followed by silence is worse than no text at all.

The consent rules

None of this is legal advice. It’s what the rules say, and how we set things up so a client stays on the careful side of them.

Federal law: texts count as calls

The FCC’s Enforcement Bureau put it directly in 2016: text messages sent to cell phones using an automatic telephone dialing system are subject to the Telephone Consumer Protection Act. Such texts need the prior express consent of the person receiving them, and texts that include or introduce an advertisement need prior express written consent. The FCC also notes that the sender carries the burden of proving consent.

Whether a particular texting tool legally counts as an autodialer is a question for a lawyer, and it isn’t worth betting the business on. We set the system up as if the rules apply:

• One text, about the call they just made. No coupons, no “while you’re here, ask about our specials”. The person called you; the text answers that call.
• Your business name in the text. The person should know who is writing without guessing.
• STOP works, every time, right away. The FCC’s rule at 47 CFR 64.1200 lists replies such as “stop”, “quit”, “end”, “revoke”, “opt out”, “cancel” and “unsubscribe” as a reasonable way to revoke consent, and says a revocation must be honored within ten business days at most. There is no reason to take ten days; the system can stop on the spot.
• No marketing list by accident. A missed call is not permission to send promotions. If you want to text offers, build a separate list where people sign up and agree in writing.

Texas: sales texts now count as telephone solicitation

Texas Senate Bill 140, in effect since September 1, 2025, expanded the state’s definition of telephone solicitation to include a text or graphic message, or an image, sent by a seller to get someone to buy. A plain reply to a missed call that only asks what the caller needs is a different thing from a sales text. If you plan to send promotional texts to Texas numbers, talk to a lawyer about the state’s requirements before the first one goes out.

Carriers: A2P 10DLC registration

A2P 10DLC is the standard US carriers put in place so that business texting to US phones from regular 10-digit numbers is verified and consensual. Registration has two parts, a brand (your business) and a campaign (what you send and why). Providers ask for the business’s tax ID; an individual without one can register as a sole proprietor brand, with lower limits. A Mexican business registers with the primary tax ID for its country, which means its RFC.

One messaging provider’s documentation says unregistered traffic gets additional carrier fees. Carriers review each registration themselves, so the timeline is outside anyone’s control, including ours. Register under your own business, so the number and its history stay with you.

10DLC covers texting to US numbers only.

WhatsApp: a different set of rules

For the Juárez side of the border, WhatsApp usually matters more than SMS. Its rules are stricter about the first message. WhatsApp’s Business Messaging Policy says you may contact people only if they gave you their number and agreed to receive messages from you.

There’s also a timing rule. Meta’s documentation says a 24-hour customer service window opens when a person messages your business on WhatsApp (or taps an ad that opens a WhatsApp chat). Outside that window, a business can send only approved template messages. A phone call opens no window. So “missed call, WhatsApp back” needs the caller’s opt-in first and a template message, which is why the simpler setup runs the other way around: the voicemail greeting and your website invite callers to message you on WhatsApp, and once they do, you can answer freely for 24 hours.

The ROI logic, without made-up numbers

You’ll find percentages online for how many callers won’t leave a voicemail and how many reply to a text. We don’t use them, because none of them was measured on your phone line. The math is simple enough to do with your own numbers:

Value per month = missed calls from new customers × share who reply × share of those who book × profit on an average job

How to fill in each piece:

• Missed calls from new customers. Your phone provider or business phone app keeps a call log. Count the missed calls in a normal month, then take out spam, repeat calls from the same number and existing customers who would have called back anyway.
• Share who reply and share who book. Nobody knows these for your business until you run it. Turn it on for 30 to 60 days and count from the inbox.
• Profit on an average job. From your own records: what an average job leaves you after materials and labor, not the ticket price.

Then the break-even question: how many booked jobs a month cover the monthly cost of the setup and the texting? Divide the monthly cost by the profit on one job. If one booked job a month covers it, the decision is easy. If it takes ten, look harder at how many new customers really miss you each month.

There’s also a value the formula leaves out: fewer hours spent calling back numbers that never pick up.

When it isn’t worth it

• You or your staff already answer nearly every call during business hours.
• Most of your callers are businesses calling from desk phones.
• Nobody will answer the texts quickly. A fast automatic text followed by a slow human is a broken promise.
• Most of your callers are in Mexico and prefer WhatsApp. Put the effort into WhatsApp instead.

Setting it up right

• Register for 10DLC under your business, with the number in your name.
• Write the text in plain words, in the language your callers use. Bilingual is fine if it stays short.
• Send one text per missed call, not a sequence.
• Use different wording for after-hours calls, so nobody expects a reply at midnight.
• Send replies to a person, or to an AI receptionist that answers calls and chats and books appointments.
• Keep a record of who opted in, who opted out and when.

How Rodco Systems handles this

Missed call text back is part of our CRM and automation work. We build it in accounts that belong to you, as a reply to the person who just called, with STOP honored automatically. Promotional texts go only to people who signed up for them. Each client registers its own business for 10DLC, and the number registration and customer data stay yours. For customers in Mexico we set up WhatsApp with its own opt-in.

Rodco Systems, El Paso, Texas.