How to give an AI agent a phone number
A phone-capable agent needs three pieces: a phone number (telephony), speech-to-text and text-to-speech, and an LLM in a real-time loop. You can buy all three in one platform or put them together yourself.
- All-in-one voice agent platforms: Vapi, Retell AI, Bland AI, and Synthflow (no-code).
- Phone numbers and calling: Twilio provides phone numbers plus voice and SMS APIs.
- Build it yourself: LiveKit (real-time audio plus an agents framework) and Pipecat (open source), with voices from ElevenLabs.
Options at a glance
| Tool | What it does | Pricing | License |
|---|---|---|---|
| Vapi | Platform for building voice AI agents with phone numbers | Usage-based (per minute) | Proprietary |
| Retell AI | Voice agents for inbound/outbound calls | Pay as you go (per minute); $10 free credits | Proprietary |
| Bland AI | AI phone calling agents for enterprises | Free start; $0.14/min usage | Proprietary |
| Synthflow | No-code voice AI agents for phone calls | Paid; enterprise from $30,000/yr | Proprietary |
| Twilio | Phone numbers voice and SMS APIs | Usage-based; free trial | Proprietary |
| LiveKit | Realtime audio/video infra and Agents framework | Free tier; paid from $50/mo | Open source |
| Pipecat | Open-source framework for voice and multimodal agents | Free (open source) | Open source |
| ElevenLabs | Text-to-speech and conversational voice agents | Free tier; paid subscriptions | Proprietary |
We list what each vendor's own site says. Pricing changes often, so check it on the vendor's site before you commit.