Best AI phone agents
An AI phone agent can mean a developer platform you build on, or a feature bundled into a business phone system. Compared on real cost per minute for each.
Retell AI wins for a team that wants to build a custom AI phone agent with predictable, itemized cost. JustCall's AI Voice Agent wins instead for a team that already uses JustCall for calling and texting and wants an agent bundled in without standing up a separate developer platform, at a real premium per minute.
The short answer
- Vapi's $0.05/minute platform fee is an orchestration charge only; the model, speech-to-text, text-to-speech and telephony are billed separately, usually landing a real call at $0.07-$0.25/minute, per vapi.ai/pricing.
- Retell AI itemizes its cost: $0.055/min voice infrastructure plus $0.015-0.040/min text-to-speech and $0.003-0.32/min for the model, landing at $0.07-$0.31/min all in, with $10 in free credit for new accounts, per retellai.com/pricing.
- JustCall's AI Voice Agent costs $0.99/minute pay-as-you-go, or $99/month for 100 minutes on its Lite package, both well above the per-minute cost of a dedicated voice-AI developer platform, per justcall.io/pricing.
AI phone agent options compared
| Option | Real cost per minute | Product type | Free tier | Best for | Not for |
|---|---|---|---|---|---|
| Vapi | $0.07-$0.25/min all-in (est.) | Developer platform, assemble your own stack | 60+ minutes included on Build | A technical team wanting full control of every component | A business wanting a finished agent with no assembly |
| Retell AI | $0.07-$0.31/min all-in | Developer platform, itemized components | $10 free credit, 20 free concurrent calls | A team that wants predictable, visible per-minute cost | A business wanting calling bundled with texting in one product |
| JustCall AI Voice Agent | $0.99/min pay-as-you-go, or $99/mo for 100 min | Add-on feature inside a phone/texting suite | None confirmed | A JustCall customer wanting an AI agent without a separate platform | Cost-sensitive use at real volume; per-minute cost is far above dedicated platforms |
Figures checked on vapi.ai/pricing, retellai.com/pricing and justcall.io/pricing, September 2026.
How the three differ in practice
Vapi
Full control over the model, voice provider and telephony layer, billed at cost or free if you bring your own API key for the model. That flexibility is real work: someone has to assemble and maintain the call flow before it does anything useful. Not for: anyone who wants a phone agent live without engineering time.
Retell AI
The most transparent per-minute breakdown of any voice platform checked: voice infrastructure, text-to-speech and model costs are each listed separately, so you can estimate real cost before building. The $10 free credit and 20 free concurrent calls are enough to prototype a real flow. Not for: a business that wants a phone number and texting bundled with the agent.
JustCall AI Voice Agent
The only one of the three that comes packaged inside a broader communication suite, so a team already paying for JustCall's calling and texting gets an AI agent without adopting a second platform. The tradeoff is cost: $0.99/minute pay-as-you-go is roughly 3 to 14 times the per-minute rate of Vapi, Retell or Bland's underlying platforms. Not for: high call volume where per-minute cost dominates the decision.
When none of these is the answer
If your call volume is low enough that a person can handle it, a human answering the phone is usually still cheaper and more reliable than standing up an AI phone agent. These platforms earn their cost at real volume, not for a handful of calls a week.
SalesCrew is not included in the ranking above because it does not build AI phone agents; it runs outbound calls through Vapi as one channel and logs the outcome against a contact. A full AI phone agent product, with inbound routing and receptionist behavior, is on SalesCrew's roadmap, not shipped.
Questions
- What's the cheapest AI phone agent per minute?
- Vapi's platform fee is the lowest headline number at $0.05/minute, but that covers orchestration only; add a model, speech-to-text, text-to-speech and telephony and a real call typically lands at $0.07-$0.25/minute. Retell AI is more itemized, landing at $0.07-$0.31/minute all in.
- Is JustCall's AI Voice Agent the same kind of product as Vapi or Retell?
- No. Vapi and Retell AI are developer platforms for building a custom voice agent from components. JustCall's AI Voice Agent is a feature inside a broader business phone and communication suite, priced as an add-on at $0.99/minute pay-as-you-go or a monthly package like $99/month for 100 minutes.
- Can an AI phone agent make outbound cold calls?
- Whether it's allowed depends on consent rules like TCPA in the US, not only the platform. Bland AI has published its own position that AI voice classified as 'artificial' under TCPA generally cannot be used for cold outbound without prior express written consent, framing its product as better suited to following up with leads who already engaged rather than cold outreach.
- Does an AI phone agent need a CRM behind it?
- It needs somewhere to log the outcome and act on it, whether that's a CRM, a spreadsheet, or a database you build yourself. None of the platforms compared here include a full sales pipeline; they handle the call, not what happens with the lead afterward.