How AI Phone Agents Work, in Plain English

Not a Phone Tree

If you've ever called a company and heard "Press 1 for sales, press 2 for support, press 3 for billing," you know what an IVR (Interactive Voice Response) system is. Most people would rather not deal with one.

AI phone agents work differently. Instead of pressing buttons through a menu, callers just talk, the way they would to a person. The AI works out what they're asking, answers out loud, and keeps the conversation going based on what the caller says.

The Three Layers of a Modern AI Phone Agent

LiveKit describes a voice agent as three parts working together.

Speech-to-text (STT). The caller speaks, and the system turns their audio into text as they talk.

Large language model (LLM). This part reads the text, works out what the caller wants, and writes a reply. It is given your business details, like your services and prices, your hours, and what counts as urgent for your shop, so the reply fits your business.

Text-to-speech (TTS). The reply is turned back into a spoken voice and played to the caller.

What Happens During a Typical Call

Here's the flow of a typical call to a VocaDent assistant.

1. Nobody at the shop picks up, so the call forwards to the AI.

2. The AI opens with a short disclosure and then your greeting, for example "Hi, you've reached the virtual assistant for Sunshine Plumbing. I'm an AI, and this call may be recorded. How can I help?"

3. The caller explains the problem. "I have a leaking water heater and need someone out today."

4. The AI takes down the caller's name, number, service address, and what's wrong.

5. If they ask about pricing, it quotes only from the prices you gave it and says the team will confirm anything else. If the caller reports a gas smell, fire, or someone hurt, it tells them to get safe and call 911 first.

6. After the call, the transcript lands in your dashboard with a priority flag. If the call was urgent, you get an email the moment it ends.

Why Speed Matters

People notice pauses on the phone. Research in Frontiers in Psychology links gaps of 700 milliseconds or more between turns with reluctant or unwelcome replies, so a slow answer can sound like hesitation.

Early AI phone systems often took several seconds to respond. LiveKit's guide says that with streaming across all three layers, end-to-end latency under 1 second is possible, which is close to the pace of a normal conversation.

Setting It Up for Your Shop

A phone agent is only useful if it knows your business. On the VocaDent pilot, William sets up your assistant with you. He needs a few things.

• Your business name and the greeting callers should hear after the disclosure
• Your hours and your service area
• The services you offer and what you charge
• What counts as urgent for your shop, like no heat in winter or an active leak

When something about your business changes, tell William and he updates it.

What AI Phone Agents Can't Do (Yet)

Here is where today's AI phone agents do well.

• Answering routine questions about hours, service area, services, and prices
• Taking down caller details for follow-up
• Flagging the urgent calls
• Picking up at night and on weekends, when nobody else can

And here is where they still struggle.

• Emotional conversations where the caller needs a person
• Calls with several people on the line
• Anything that needs a back-office system the AI isn't connected to (VocaDent offers Google Calendar booking on request while it is in beta; bookings into other systems still go through your team)

The point is that a caller gets an answer instead of voicemail, and your team calls back the people who need a person.