How to Set Up Missed Call Text Back With AI Follow-Up (GoHighLevel or Twilio + n8n)

Missed call text back with AI follow-up

A homeowner with a leaking water heater calls three plumbers. The first one does not pick up. Thirty seconds later that homeowner gets a text: "Sorry we missed you, this is Dave's Plumbing. What's going on? We can usually get someone out today." They reply to that text, and they never hear the other two plumbers' voicemail greetings.

That is the whole idea behind missed call text back. The basic version is decades-old SMS technology. What changed is that an AI can now carry the conversation from there: ask what the job is, get the address, offer two time slots and put the booking on your calendar while you are under a sink. This guide shows how to build both parts this week, on GoHighLevel if you want it done in an hour, or on Twilio and n8n if you want to own it and pay less.

Why speed matters more than the message

The case studies on this site keep landing on the same finding. A landscaping company that put an AI on every inbound lead cut its response time from 30 to 60 minutes down to under 60 seconds, and its lead-to-booked-estimate rate rose 42 percent in the first two weeks (builtwithagents.ai/strategy/instant-ai-lead-response-local-service-businesses). The owner was careful to say that is early data from two weeks. Across four local service clients running a set of small OpenClaw agents, average lead response fell from more than 6 hours to 4 minutes, and one three-person plumbing company went from responding to 30 percent of its leads to 94 percent with the same ad spend (builtwithagents.ai/strategy/19-openclaw-agents-local-service-businesses-8-dollars-month).

Neither result came from clever copy. It came from replying before the customer moved on. Google says the same thing in its own way: its Local Services Ads help page lists responsiveness as a ranking factor and states that missed calls may hurt it.

What a good missed call text back system does

There are four parts, and most setups only build the first one.

First, the instant text. Within seconds of a missed call, the caller gets a short, human-sounding message from your business. Second, the AI reply handler. When the caller texts back, an AI asks the two or three questions you would ask (what is the problem, where are you, when works) and offers real times from your calendar. Third, the stop rule. If they do not reply, they get one follow-up at most, then nothing. Fourth, the human handoff. Anything urgent, angry or confusing goes to a person immediately, with a summary.

Option A: Set it up in GoHighLevel

GoHighLevel (HighLevel) is the fastest route because missed call text back is a built-in phone setting. As of October 2026 its plans start at $97 a month with a 14-day free trial.

Step 1: Get a number and register for A2P 10DLC

Buy a local number in HighLevel's LC Phone, which costs $1.15 a month. Then complete A2P 10DLC registration in the phone settings. This is not optional. Twilio, which runs LC Phone underneath, blocks business texts from unregistered local numbers, and you will see them fail with error 30034. HighLevel lists low-volume registration at $22.50 one-time plus $1.50 to $10.50 a month per campaign as of October 2026. Approval takes time, so start this first.

Step 2: Point your calls at the new number

You have two choices. Port your main business number into HighLevel, or keep your current number and use conditional call forwarding so only unanswered calls go to HighLevel. On Verizon, for example, dialing *71 followed by the destination number turns on No Answer/Busy Transfer, and *73 turns it off. Other carriers have similar codes; check yours. Forwarding is the lower-risk way to start because nothing about your current phone setup changes.

Step 3: Turn on missed call text back

In your sub-account, go to Settings, then Phone System, then Voice, then Voicemail and Missed Call Text Back. Tick Enable Missed Call Text Back, click Customize, and write your message in the Enter message field. Set the incoming call timeout slider to between 10 and 20 seconds, which is the range HighLevel recommends. Save.

Step 4: Write a first text that gets a reply

Keep it under 160 characters so it sends as one segment, name the business, ask an open question and include an opt-out. A version that works for trades: "Hi, it's Dave's Plumbing. Sorry we missed your call. What can we help with? We often have same-day slots. Reply STOP to opt out." Twilio's messaging policy expects opt-out language in your first message, and the word STOP must work.

Step 5: Turn on Conversation AI for the replies

HighLevel's AI Employee is $50 a month per location for 1,000 agent responses or $97 for unlimited use, as of October 2026. Turn on Conversation AI for SMS and connect it to your booking calendar. Give it a tight brief: "You are the scheduling assistant for Dave's Plumbing in Tulsa. Ask what the problem is, the service address, and whether today or tomorrow works. Offer two open slots from the calendar. Never quote a price. If the customer mentions flooding, sewage, gas or no water at all, say a technician will call within 10 minutes and stop." Start in a mode where it drafts replies for you to approve, read a week of conversations, then let it reply on its own.

Step 6: Stop the double texts

HighLevel's own help article notes that the feature texts on every missed call, so a customer who calls three times gets three texts. Its suggested fix is to edit the missed call recipe in Workflows and add a wait step of around 20 minutes, or tag contacts after the first text and skip anyone already tagged. Do this before you go live.

Option B: Build it on Twilio and n8n

If you already use n8n, or you are building this for clients, Twilio plus n8n costs less and gives you full control.

Step 1: Buy a Twilio number and register it

A local Twilio number is $1.15 a month. Register a brand and campaign for A2P 10DLC in the Twilio Console. Twilio's published fees are a one-time brand fee, a $15 campaign vetting fee and a monthly campaign fee from $1.50 to $10; fees changed in August 2025, so check the exact figures in your console.

Step 2: Ring your phone first, then report the result

Point the Twilio number's voice webhook at a small TwiML response that uses Dial to ring your cell or office line, with a timeout of 15 to 20 seconds and an action URL set to an n8n webhook. When the dialed call ends, Twilio sends that webhook a DialCallStatus value. Completed means someone answered. No-answer, busy and failed mean the caller did not reach you.

Step 3: Send the text from n8n

In n8n, start the workflow with a Webhook node, add an If node that passes only no-answer, busy or failed, then a Twilio node that sends your first message to the caller's number. Add a check against a Google Sheet or database so the same number is not texted twice within a day.

Step 4: Let an AI Agent node handle replies

Set the Twilio number's messaging webhook to a second n8n workflow. Use an AI Agent node with your scheduling brief as the system prompt, a memory node keyed on the phone number so it remembers the thread, and a Google Calendar or Cal.com tool so it can check availability and book. A small model is plenty for this. OpenAI lists gpt-5-mini at $0.25 per million input tokens and $2 per million output tokens as of October 2026, so a ten-message conversation costs well under a cent.

Step 5: Alert a human

Add a branch that texts or Slacks you a summary whenever the AI books a job, the customer uses an urgent word, or the AI says it is not sure. If you want the AI to call the lead back instead of texting, one builder on this site wires n8n to Vapi to place an outbound AI call the moment a form comes in (builtwithagents.ai/strategy/nate-herk-ai-voice-agent-calls-every-new-lead-n8n-vapi).

What it costs

On GoHighLevel, expect $97 a month for the Starter plan, $50 or $97 for the AI Employee, $1.15 for the number, and text messages at $0.00747 per segment plus carrier fees, as of October 2026. Call it $150 to $200 a month all in for a single business. Agencies spread the platform fee across clients, which is why so many of the home service builds on this site run on HighLevel.

On Twilio and n8n, a number is $1.15 a month and outbound texts are $0.0083 per segment plus a carrier fee of $0.0035 to $0.005, as of October 2026. A hundred missed calls a month with four messages each comes to about $5 in texts. n8n Cloud Starter is 20 euros a month for 2,500 executions, or you can self-host the free Community Edition on a small server. The AI model adds pennies. Most single-business builds land between $25 and $40 a month after the one-time 10DLC fees.

What breaks, and when not to bother

Texts to landlines go nowhere. If many of your callers are businesses calling from desk phones, a text back will miss them, and a quick callback is still the better fix.

Emergencies need a voice. A gas smell or a flooded basement should not sit in a text thread. Make sure your urgent-word branch rings a person, and consider a voice receptionist for after-hours calls. Our guide to AI receptionist costs covers that option.

Follow-up sequences can cross the line. Twilio's messaging policy says that when a customer contacts you, you can respond in that exchange, but that does not cover ongoing marketing. One reply and one nudge are a conversation. A seven-day drip to someone who called once is a marketing campaign, and it needs consent. Honor STOP immediately.

And if you already answer nearly every call, this adds little. Pull your call log first. If you miss fewer than a handful of calls a week, fix the gaps in coverage before you add software.

Frequently Asked Questions