Build a ChatGPT-Powered Phone Assistant with Twilio’s call-gpt (in Under 2 Hours)

If you’ve ever wanted to give ChatGPT a voice—and a phone number—Twilio’s open-source call-gpt project delivers exactly that. In just a couple of hours, you can spin up a fully functioning AI voice assistant capable of answering calls, holding contextual conversations, handling interruptions, and even triggering external tools. It’s slick, simple, and shockingly powerful.

But what is call-gpt, really? And how does it stack up against Twilio’s own newer offerings like Twilio CustomerAI?

Let’s dive in.

The Backstory: Twilio’s Open-Source Gift to AI Devs

Twilio launched call-gpt under its twilio-labs umbrella—a GitHub org that experiments with bleeding-edge integrations and gives devs hands-on access to tools before they become polished products. The repo quickly gained traction, with nearly 500 GitHub stars and rising. It’s one of the most popular projects Twilio Labs has released.

At its core, call-gpt is a minimalist yet powerful integration between:

• Twilio Programmable Voice
• OpenAI’s ChatGPT API
• Deepgram for real-time transcription

By leveraging streaming responses, the system delivers low-latency, interruptible audio replies—creating a surprisingly natural phone experience with AI. While Twilio has been pushing commercial solutions like CustomerAI, this project feels like their “dogfooding” moment—testing the waters of LLMs in a public playground.

That said, unlike Twilio Studio—their visual builder—call-gpt gives developers raw code access. That means full control, easier customization, and smoother integration into your own tools.

And if you care about performance: deploy it to Fly.io’s Virginia region. You’ll get sub-second responses with less hiccuping—based on our own testing.

How It Works (Visually)

[📞 Caller]
↓
[Twilio Webhook ➝ /incoming]
↓
[Fly.io App: call-gpt]
↓
[Deepgram → OpenAI (ChatGPT)]
↓
[Response streamed back to Caller 🔊]

Modify the AI’s Personality

The real power of call-gpt is in gpt-service.js. This is where you define how your assistant sounds, thinks, and interacts.

Example snippet:

// On line ~18, in gpt-service.js
this.userContext = [
  {
    role: "system",
    content: "You are a cheerful personal assistant for Megabyte Labs. Keep replies short, friendly, and helpful."
  },
  {
    role: "user",
    content: "Can I speak to someone about your open-source tools?"
  }
];

Want it to be a receptionist? A sassy help desk agent? A poetry-reading chatbot? It’s all just a few lines of code away.

Why Not Use Twilio Studio?

Twilio Studio is great for quick bots and menus, but for real-time streaming conversations with ChatGPT—Studio can’t compete. By all means though, correct me if I am wrong in the comments!

Here’s why call-gpt wins:

Real-World Use Cases

🧑‍⚖️ Small Business Receptionist

Handle calls, take messages, and answer FAQs—all AI-powered and 24/7.

🧑‍💻 Solo Developer Inbox

Let callers leave voice messages, screen leads, or get info while you focus.

🎓 Voice-Driven AI Demos

Perfect for labs, students, or startups demoing LLM interactions over voice.

📞 Customer Data Integrator

Match the caller’s phone number to a CRM record and respond contextually.

Setup in Minutes

1. Fork the repo → https://github.com/twilio-labs/call-gpt
2. Rename config files:
   fly.toml.example → fly.toml
.env.example → .env
3. Populate .env with Twilio, OpenAI, and Deepgram keys
4. Upload your secrets to Fly.io: fly secrets import < .env
5. Customize services/gpt-service.js to fit your use case
6. Deploy it: fly deploy
7. Link your Twilio number to https://your-app.fly.dev/incoming

Feature Highlights

• Low-latency responses (~1s with Virginia region)
• Natural interruptions
• Memory within a conversation
• Tool and API calling support
• Recording + transcription support
• Backed by a trusted, public company (Twilio)

Try It Yourself

Call our demo line: (469) 694-3696
And talk to our AI assistant—powered by Twilio, OpenAI, and Deepgram.

Final Thoughts

When it comes to OpenAI phone integration, Twilio remains the king of telephony infrastructure. Combine that with OpenAI’s reasoning and Deepgram’s transcription, and you’ve got an incredibly powerful tool for individuals and businesses alike.

This setup is elegant, reliable, and surprisingly developer-friendly. It may not have the polished GUI of Twilio Studio or the enterprise integrations of CustomerAI—but in the hands of a creative dev, call-gpt could very well outperform both.

This blog is about slayers: Twilio, OpenAI, and Deepgram—a triple-threat stack for the voice-first AI future.

Stock tip? Twilio.
Casino pick? Red.
AI phone system? call-gpt, hands down.

Watch the setup video walkthrough (same as video shown at the beginning of the article)