Docs · Phone calls
Phone calls: let your agent answer and make calls
Updated September 25, 2026 · by Nishanthan Janarthanarajah (Nishy), founder of Agent Studio
Setup in four steps
- Deploy the agent. Calls always run the live version.
- Open Phone in the builder header, pick a language, a voice and a greeting.
- Find a number by country and press Use. It is attached to this agent and answers immediately.
- Press Call me to hear it, then turn Answer calls on for real callers.
What happens on a call
The greeting plays, the caller speaks, and the agent answers in one to three short sentences written for speech: no lists, no links, numbers said aloud. Callers can interrupt at any time. Every turn, tool call and guardrail decision is recorded in the trace, and the whole transcript is kept with the call.
The four-minute rule
A call runs for up to five minutes. At four minutes the agent says the call is nearly out of time and, if it has a number, offers to call back. On a yes it hangs up and calls back right away with the earlier conversation loaded, so the caller carries on where they left off. Callers can also simply ring again.
Minutes per plan
| Plan | Voice minutes per month | Phone number |
|---|---|---|
| Free trial | 5 | No |
| Starter | 20 | Yes |
| Pro | 40 | Yes |
| Growth | 1000 | Yes |
| Agency | 2500 | Yes |
Minutes count inbound and outbound calls across all of your agents, by Twilio's billed duration. When the month's minutes are used up, new callers hear a short message and the agent stops answering until the next month.
Numbers and countries
United States, United Kingdom, Canada, Australia, India, the United Arab Emirates, Singapore, Germany and Sri Lanka are available from the panel. Sri Lanka offers mobile and toll-free numbers and needs regulatory documents on file first. Outbound calls to Sri Lankan phones cost more per minute than most countries, so prefer inbound for Sri Lankan callers.
Related: traces, guardrails, sub-agents and linked agents.
Frequently asked questions
How does a call reach my agent?+
Twilio answers the number and streams the caller's speech to Agent Studio as text. Your deployed agent runs exactly as it does for the API, with the shield, guardrails, sub-agents and tools, and its answer is spoken back with the voice you chose. Each turn is a run in the agent's traces.
Why does the agent wrap up at four minutes?+
Each call runs on a connection with a five-minute limit. At four minutes the agent tells the caller, offers to call them back, and closes politely. If the caller says yes, it calls back from the same number within seconds and continues with the earlier conversation loaded.
Can I get a Sri Lankan number?+
Yes: mobile (+947) and toll-free numbers. Twilio requires a business registration document and, for mobile numbers, a Sri Lankan address on file before the first purchase. Once your regulatory bundle is approved, numbers can be bought from the Phone panel.
Which voices can I use?+
Any ElevenLabs voice id, or Google and Amazon Polly voices, through Twilio. The Phone panel lists a curated set; paste another id to use it.
What does a call cost me?+
Voice minutes are included in your plan. Twilio bills you directly for the number and the call itself when you connect your own Twilio account.