How to Build an AI SMS Follow-Up System for Under $20/Month
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AI Avengers Lab members get the full working setup: pre-built code, campaign scripts, and weekly live builds. $89/mo.
See what's inside the LabIn January I was paying $1,100/month to GoHighLevel. The SMS campaigns were a big part of why. We had 3,000 contacts and an active follow-up sequence running. When I pulled the actual delivery and response rates, the numbers were embarrassing. 71% delivery rate. 3.2% response rate. And GHL kept adding SMS credits to my bill every time I hit a limit.
Three months later I rebuilt the entire system on Twilio direct with Claude handling response personalization. My monthly SMS cost: $14. Response rate: 8.7%. The rebuild took one weekend.
Why Direct Twilio Beats Platform SMS
When you send SMS through GHL, you are on a shared sending pool with thousands of other businesses. Carriers have seen this pattern before. Shared pools get flagged faster. Delivery drops. GHL charges you for the attempt whether it delivers or not.
With Twilio direct, you own your phone numbers ($1/month each), you control your sending patterns, and you have direct carrier relationships. Twilio's A2P 10DLC registration costs $4 one-time plus $10/month brand registration. After that, you are sending at $0.0079 per message - roughly $15 for 1,900 messages.
The 3-Step AI Follow-Up Sequence
Here is the exact sequence I run. All personalization is handled by Claude via API before the message sends.
Message 1 (immediate after form fill): Short, specific, first-name only. Reference what they signed up for. Ask one yes/no question. Example: 'Hey [Name], saw you grabbed the AI stack guide. Is your main goal cutting software costs or building new revenue?' Under 60 words. No links.
Message 2 (Day 2 if no response, or Day 1 reply triggers this): Branch based on their answer. Claude reads the reply and selects the appropriate next message from your library. The branching logic is a simple if/else in your webhook handler. If they said 'costs', send the sovereign stack breakdown. If they said 'revenue', send the agency build story.
Message 3 (Day 5 if still cold): Soft close with low friction. 'Still happy to answer questions - just reply back. Here is where to learn more when you are ready: [link].' One link. One ask. Done.
Technical Setup: What You Actually Need
Twilio account: Free to start, pay as you go. Register a local number ($1/month). Complete A2P 10DLC registration ($4 one-time + $10/month). This is not optional - unregistered numbers get blocked by carriers.
Webhook handler: A simple Node.js or Python script that receives form submissions, calls Claude API to personalize the first message, then triggers Twilio send. Host it on Railway or Render for free. The whole script is under 80 lines of code.
Claude API: The $20/month Claude Pro is not what you use for API calls. You use claude.ai API keys, billed at usage - roughly $0.003 per message personalization. For 500 messages/month that is $1.50. Nearly free.
Compliance Is Not Optional
Every contact must opt-in explicitly before receiving SMS. Your form needs a checkbox: 'I agree to receive SMS messages from [Business]. Reply STOP to opt out.' Store opt-in timestamp and source in your database. Honor every STOP reply within 5 minutes - Twilio has a built-in opt-out handler you enable with one config toggle.
This is not about being nice. TCPA violations are $500-$1,500 per unsolicited message. Get the opt-in right.
The full technical build guide - including the webhook script and Claude prompt templates - is inside AI Avengers Lab at aiavengers.team/lab. Founding members get access to every build we run, including this one.
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Frequently Asked Questions
What is A2P 10DLC and do I really need it?
A2P 10DLC is the US carrier registration system for business SMS. It stands for Application-to-Person, 10-digit long code. Without it, your messages get filtered or blocked by major carriers. Registration costs $4 one-time and $10/month. It is mandatory if you send more than a handful of messages.
Can I use this system if I am not technical?
The webhook handler requires basic coding or someone who can set it up once. If you have no coding background, make.com or Zapier can replace the custom webhook for many use cases, adding about $10-20/month. The Twilio side is all point-and-click configuration.
How does this compare to GHL SMS in terms of deliverability?
With dedicated local numbers and proper A2P registration, Twilio direct consistently outperforms shared platform sending pools. Most businesses see 10-20% improvement in delivery rates after switching. The response rate improvement comes from AI personalization of message content.
What if someone replies with a question I did not anticipate?
Set up an escalation trigger: if Claude's confidence in the response is below a threshold, or if the reply contains specific keywords (price, legal, refund), route to a human review queue and send a holding message: 'Great question - I will have a personal answer for you within 24 hours.'
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Creator of AI Avengers Lab. Building sovereign AI stacks for business owners and professionals- no npm, no SaaS middleware, just Claude Code and direct API connections.