Answering calls with AI: how it works and what you need

Answering calls with AI means connecting a business phone to a voice agent built on language models that picks up, talks in a natural voice, answers with the business's information, takes details and books appointments. It is set up with a dedicated number or by diverting calls from your current number, with no need to change provider.

The technical flow: the call comes in over IP telephony (SIP), the audio is transcribed in real time, a language model writes the reply using the business's knowledge base, and a synthetic voice speaks it. The whole cycle takes under a second per turn, which keeps the conversation natural.

The three usual ways to connect it: a new dedicated number (the simplest), unconditional diversion (the AI answers every call and passes on the ones that need a person) or conditional diversion (the AI only steps in if you're on another call, don't answer or it's outside opening hours). The last one is the typical starting point: the AI only picks up what you're missing today.

An applied example

A hair salon turns on conditional diversion: if nobody answers within 5 rings or the line is engaged, the AI steps in. In practice, quiet periods carry on as before, but the 2:30 pm call (when the salon is full) is no longer lost: the AI books the appointment and the owner sees it confirmed in her diary.

When it is worth it

Your phone rings when you can't answer it: you're with clients, driving or outside opening hours.
The line is often engaged because there's only one line and one person.
Missed calls don't get returned, or get returned late, and you know it.
Most calls are to book an appointment or ask the usual questions.

Common mistakes

Using it for cold outbound calls. Outbound AI calling without prior consent can lead to fines in Spain; answering inbound calls, by contrast, is safe.
Not telling callers they're speaking to an AI, or not explaining how their data is handled (GDPR).
Not reviewing the conversations in the first few weeks. That's where you fine-tune answers, tone and edge cases.
Setting the AI up to try to solve absolutely everything. It should know how to say 'I'll put you through to the person in charge' and take a message.

How we do it at STAKKER

STAKKER SYSTEMS offers this as a product (STAKKER Voz): your own number, AI trained on your data, bilingual, with handover to a human and delivery of appointments and leads. The quickest way to try it: message us on WhatsApp at +34 951 870 512 and see for yourself how our AI sales assistant replies, live in production. Free diagnosis and a demo with your data before you pay.

Frequently asked questions

Do I have to change provider or number?

No. The usual approach is to add a dedicated number for the AI or set up a diversion from your existing number. Your line and your provider stay untouched.

What happens to calls the AI can't handle?

It hands them over: it transfers the call to a person if one is available, or takes a message with the customer's details and sends it to the business straight away. No call is left hanging.

How many calls can it handle at once?

Several in parallel, which is exactly what a single line with one person can't do. The exact capacity depends on the telephony setup in each case.

Does it work in several languages?

Yes. Today's voice agents handle Spanish and English well within the same call, detecting the caller's language. Handy in tourist areas or with international customers.

Related terms

AI virtual receptionistAn AI virtual receptionist is a voice system that answers your business calls in a natural voice, trained on your business's real information: it answers questions, takes the caller's details, books appointments and hands over to a person when the conversation calls for it. Unlike an answerphone or a phone menu, it holds a real conversation, 24/7.
AI customer serviceAI customer service is a layer of voice and chat systems, built on language models, that answers a business's calls and messages: it handles common questions, captures the details of interested customers, books appointments and hands over to a person anything that needs judgement. Its value isn't in replacing your team, but in covering what currently goes unanswered.
AI phone agentAn AI phone agent is a system that answers (or makes) phone calls using a natural synthesised voice, understands the caller in real time, holds a coherent conversation and carries out actions (booking appointments, logging leads, transferring calls). It works 24/7 and handles several calls at once with no queues.