How to Build an AI Voice Agent That Handles Client Calls 24/7

How to Build an AI Voice Agent That Handles Client Calls 24/7 Missed calls cost businesses money. A dental clinic missing 10 calls a day at $150 average ticket loses $1,500/day — $547K/year. That's not a staffing problem. That's a systems problem. Here's exactly how to build an AI voice agent that answers, qualifies, and books appointments — no code needed for the basics, some JS for the advanced version. What You're Building An AI phone agent that: Answers calls in under 2 seconds, 24/7 Speaks naturally (not robotic IVR) Qualifies callers (new vs. returning, urgency) Books appointments directly into your calendar Sends a WhatsApp confirmation after the call Stack: Vapi (voice AI) + Cal.com (scheduling) + Twilio (phone number) + optionally a small Node.js webhook. Step 1: Set Up Your Vapi Account Vapi.ai handles the hard parts — real-time transcription, text-to-speech, interruption handling, and tool calling. Create an account at vapi.ai Go to Assistants → Create Assistant Choose Phone