CallBooker vs Retell AI

Two fact sheets from our own research, side by side — pricing, platforms, API access and status re-checked by us rather than quoted from the vendors.

The short answer

Entry price: CallBooker from $39/mo, Retell AI from $0.07/min — different billing units, so no direct winner
Free plan: Both have one
Public API: Both have one
Higher Trust score: Retell AI — 94 vs 82 for CallBooker
Best fit: CallBooker: Sales teams that lose leads because nobody calls back within minutes · Retell AI: Teams replacing an outbound qualification or booking script

From our own records as of each tool's last check. Anything we have not confirmed is left out rather than guessed. How we verify

CallBookerAI voice agents that call new leads within seconds, handle objections and book meetings into Google Calendar or Calendly.

Retell AIBuild and run AI phone agents that book, qualify and transfer calls, billed by the minute.

Side by side

Fact	CallBooker	Retell AI
Category	Voice Agents & Phone AI	Voice Agents & Phone AI
Pricing model	Freemium	Freemium
Starts at	$39/mo	$0.07/min
Public API	Yes	Yes
Trust score	82 / 100	94 / 100
Platforms	Web, API	Web, API
Company	CallBooker	Retell AI Inc.
Launched	—	2023
Last verified	Oct 15, 2026	Sep 6, 2026

What our research says

CallBooker

CallBooker is no longer the inbound receptionist its earlier marketing described: it now dials outbound, calling new leads within seconds and booking them into a calendar, and the pricing has been rebuilt around that with a free 10-minute trial and a $39 entry tier. Minute-based plans with no overage are easy to budget, but call carriage runs on your own Twilio account, and the operator still publishes no legal entity or address.

Pros

Free plan with 10 minutes and no card, so you can hear the agent before paying
No overage billing: calling pauses when minutes run out instead of surprising you
Lead API with webhooks plus an MCP server for managing agents from Claude or Cursor
33 languages on every tier, including the free one

Cons

You must bring your own Twilio account, which adds setup and a second bill
Only 200 minutes on the $39 tier, so a busy funnel outgrows it fast
Yearly billing is advertised but no yearly prices are shown
No legal entity, address or country beyond California governing law

Retell AI

One of the more honest voice-agent stacks: the pricing page breaks out infrastructure, TTS and LLM cost per minute so you can predict a call's cost instead of guessing. Telephony choice is wide and the concurrency allowance is generous. The catch is that per-minute billing plus add-ons makes a busy contact centre expensive fast, and the cheap end of the range only holds if you pick the cheap models.

Pros

Per-minute cost broken down by voice infrastructure, TTS provider and LLM on the public pricing page
Telephony via SIP trunking, Twilio and Vonage plus n8n, HubSpot, Make and Go High Level integrations
20 concurrent calls included before any concurrency charge
Voice, chat and SMS agents share one platform and API
HIPAA path exists via a signed BAA covered in the terms of service

Cons

Cost per minute more than quadruples between the cheapest and most capable model combinations
Knowledge base, denoising, PII removal and branded caller ID are all metered extras
No flat-rate plan, so a spike in call volume lands straight on the invoice

Which one fits

Choose CallBooker if you need

Sales teams that lose leads because nobody calls back within minutes
Clinics and service businesses that want confirmation and no-show calls automated
Teams already on HubSpot, Calendly or Zapier who want a caller wired in without code

Choose Retell AI if you need

Teams replacing an outbound qualification or booking script
Contact centres that already have Twilio, Vonage or SIP trunking
Developers who want per-minute cost visibility before launch