Building a Voice Agent Using n8n, Twilio, and SIP Integration

🧩 Introduction

In this guide, I share how I built a voice automation agent using n8n integrated with Twilio, WhatsApp, and SIP trunking (Evenlabs).
The goal was to automate real-time voice interactions through WhatsApp by routing TwiML responses over a SIP connection — since WhatsApp doesn’t directly support PSTN (Public Switched Telephone Network) calls but allows SIP-based communication.

This project demonstrates how open-source automation tools like n8n can simplify complex integrations and enable advanced voice workflows across multiple communication channels.

⚙️ Tech Stack

n8n – Workflow automation and orchestration

Twilio – Voice and messaging API

Evenlabs SIP – SIP trunking for routing voice calls

WhatsApp Business API – Customer interaction channel

AWS EC2 – Cloud hosting for production deployment

Node.js – Self-hosted n8n environment

Docker – Containerization for portability and scaling

Ngrok – Secure webhook tunneling for local testing

🧠 How It Works

Incoming WhatsApp message or call is received through Twilio’s API.

n8n captures the webhook event and processes the data.

The workflow triggers TwiML logic to route the voice flow via Evenlabs SIP.

Dynamic responses are generated (e.g., prompts, answers, status messages).

Twilio SIP handles the communication bridge while n8n manages automation logic.

Workflows are logged and monitored within the n8n dashboard.

🖥️ Hosting and Deployment

I hosted the solution on AWS EC2 for scalability and reliability.
For testing and development, I self-hosted n8n using Node.js, Docker, and Ngrok.
This setup allowed me to:

Test workflows locally with secure webhooks

Debug API requests in real-time

Seamlessly switch from local to cloud deployment

🧩 Challenges & Solutions

Challenge: WhatsApp doesn’t allow PSTN connections directly.
Solution: Used SIP trunking (Evenlabs) to bridge Twilio’s voice flow through SIP.

Challenge: Local testing for Twilio webhooks.
Solution: Integrated Ngrok for secure tunneling.

Challenge: Scaling for multiple users and clients.
Solution: Deployed on AWS and used Docker containers for portability.

💡 Key Takeaways

n8n offers incredible flexibility for building voice automation systems.

Combining Twilio, WhatsApp, and SIP trunking opens powerful communication possibilities.

With Docker and Ngrok, local development mirrors production environments easily.

This project shows how automation can bridge modern messaging with traditional voice systems.

🧾 Author

Tanaka Chindakuda
Founder, Staysure Software (Zimbabwe)
💬 Focus: Automation, AI Agents, and Workflow Systems
📧 [e-mail]