Guide · AI Receptionists
Three voice-AI platforms charge no monthly base and bundle zero minutes — so you can pay for a single test call
Vapi, Retell and Bland are the pure pay-as-you-go options here: $0/mo, no included minutes, billed per minute from the first second. Their headline rates span 2.8x — and cover different slices of the call. Synthflow, once the fourth, no longer lists its pay-as-you-go plan.
Six vendors in our dataset publish a $0/mo entry plan, but only three of them mean “no commitment” the way a usage-only buyer does: no monthly base, nothing bundled, and a meter that starts on the first connected minute. Those three are Vapi (Build), Retell AI (Pay As You Go), and Bland (Start) — every one carries a $0/mo platform fee, lists minutesIncluded as null, and bills purely per minute. A fourth, Synthflow’s Pay As You Go plan, used to belong here; last seen on 2026-06-27, it is no longer listed as of 2026-09-27, and the page now sells only sales-led Enterprise contracts that start at $30,000 annually. The other three $0/mo plans, Phonely Free (100 bundled minutes), Smith.ai Free (25 bundled calls) and My AI Front Desk Free (20 bundled minutes), are also commitment-free, but they hand you a fixed allowance rather than open-ended pay-per-use — a different offer, covered separately. If your literal requirement is “open an account, run one test call, pay for exactly that one call,” the three pure pay-as-you-go platforms are the set, because none of them includes a single bundled minute for you to leave unused.
What “what you use” costs is where they split. The marginal rate runs from $0.05/min on Vapi to $0.14/min on Bland — a 2.8x spread on the headline number alone (0.14 ÷ 0.05 = 2.8). But the bigger trap is that the three rates don’t describe the same thing.
The three zero-commitment rates, and what each one covers
| Vendor | Plan | Platform fee | Per-minute rate | What the rate includes |
|---|---|---|---|---|
| Vapi | Build (PAYG) | $0/mo | $0.05/min | Platform fee only — LLM/STT/TTS passed through at cost |
| Retell AI | Pay As You Go | $0/mo | $0.055/min floor | Voice infra only — LLM + telephony ($0.015/min) on top |
| Bland | Start | $0/mo | $0.14/min | All-in — LLM + STT + TTS + telephony |
Read the right-hand column before the price column. Vapi’s $0.05/min is a platform fee with the language model, speech-to-text, and text-to-speech billed through “at cost” on top — so $0.05 is a floor you will never actually pay in production. Retell’s $0.055/min is its voice infra alone; the vendor’s own published all-in range is $0.07–$0.31/min once you add an LLM and US telephony at $0.015/min.
Among these three, Bland’s Start plan is the only one whose per-minute rate is explicitly all-in — model, speech, and telephony included — which is exactly why it sits highest at $0.14/min. The cheapest-looking number in this group and the most honest number in this group are not the same row.
The “single test call” math makes the point concrete. Run one 3-minute test and the bill is the rate times three: $0.15 on Vapi’s platform fee, $0.165 on Retell’s infra floor, $0.42 on Bland’s all-in $0.14 — but only Bland’s $0.42 is a finished number. Vapi’s $0.15 and Retell’s $0.165 still owe you a model and telephony bill that the pricing page doesn’t total for you.
So which is actually the cheapest pay-as-you-go?
It depends entirely on whether you want to assemble a model stack. If you are a developer who will wire up your own LLM and telephony, Vapi’s $0.05 and Retell’s $0.055 are genuinely low platform taxes and the real bill lands somewhere in Retell’s published $0.07–$0.31/min band depending on the models you pick. If you want a single rate you can multiply by your call minutes and trust, Bland’s $0.14/min all-in is the figure you can take at face value — higher sticker, fewer surprises. (Which of these is cheapest per real minute once the stack is assembled is a separate question; here the point is narrower — which ones cost you nothing to open and nothing to leave idle.)
Synthflow has left the set entirely. Its $0.09 Voice Engine rate, with LLM and telephony stacked on top and reseller and concurrency add-ons ($2,000/mo white-label, $20/unit/mo extra concurrency) beside it, went with the Pay As You Go plan; what its page sells now — Enterprise contracts from $30,000 a year — is the opposite of zero commitment.
The compliance footnote that reorders the list
For a healthcare buyer the ranking changes before price does. All three — Vapi, Retell AI, and Bland — publish HIPAA support with an available signed BAA, but not on the same terms. (Synthflow, which calls out HIPAA for Enterprise only and publishes no BAA, would have dropped out of a compliant shortlist even before its pay-as-you-go plan left the page.)
And the cheapest-looking name carries the catch here too: Vapi’s BAA is a $2,000/mo add-on. The platform that starts at $0/mo and $0.05/min becomes a $2,000/mo line item the moment you need HIPAA — which inverts the entire “no monthly commitment” premise for any clinic. Bland has a gate of its own: its signed BAA sits on the Enterprise tier, not on the $0/mo Start plan. Among these three, for a regulated buyer who genuinely wants zero commitment, Retell (BAA available, $0.055/min infra floor) is the one that keeps the promise without a four-figure add-on or an enterprise contract.
How to read this
Three platforms in this dataset let you start at $0/mo with nothing bundled and pay per minute: Vapi, Retell, and Bland; Synthflow’s pay-as-you-go plan is no longer listed as of 2026-09-27. (Three more $0/mo plans — Phonely’s 100 minutes, Smith.ai’s 25 calls and My AI Front Desk’s 20 minutes — are commitment-free too, but they bundle a fixed allowance instead of billing pure usage.) The honest one-line answer is that “free to start” is real and the per-minute economics are not interchangeable — $0.05 buys you a platform fee, $0.14 buys you a finished call, and the 2.8x gap between them is almost entirely the difference between a rate you’ll assemble around and a rate you’ll actually pay. Decide whether you’re buying a building block or a working receptionist first; the cheapest column answers a different question than the one most buyers are asking.