Synthflow Alternatives

Synthflow Alternatives: 5 AI Voice Agent Tools Compared

Looking for Synthflow alternatives? This page compares Retell AI, Bland AI, Vapi, ElevenLabs (ElevenAgents) and VoiceOI on published pricing, how you build agents, telephony and compliance claims, using each vendor's own pages. It is written for teams that want to run AI voice agents on phone calls, and it is honest about where each one is a poor fit, including ours.

Disclosure: this page is published by VoiceOI, one of the tools listed. Vendor details come from each vendor's own site and were last reviewed in October 2026; check their sites for current plans.

Why Teams Look for a Synthflow Alternative

Price entry point: Synthflow's pricing page lists enterprise contracts starting at $30,000 annually, with the final price set by call volume, concurrency, telephony, integrations, security and launch support. The page we reviewed lists only the enterprise plan, with no per-minute rates.
Buying process: the same page describes a sales-led package that includes implementation, onboarding, training and launch support. The pricing page we reviewed shows only that enterprise package, so check Synthflow directly for self-serve options.
Pricing model: if your volume is high and steady, a per-minute bill and a flat per-bot bill scale differently. A per-minute example from the sources below: 10,000 talk minutes on Bland's Start plan at $0.14 is $1,400 a month before transfer time, and on Vapi the $0.05 hosting fee alone is $500 before speech, language-model, voice and telephony costs. A VoiceOI worked example sits in its entry below.
Fit for outbound sales floors: Synthflow lists inbound and outbound flows, appointment booking, voicemail detection and SMS follow-ups. VoiceOI focuses on VICIdial and SIP outbound floors where a bot qualifies the lead and a human closes.

Source: Synthflow's pricing page and homepage, reviewed October 2026.

Synthflow Alternatives Compared

Tool	Best for	Published pricing	How you build	Call types	Compliance badges on its own site
Synthflow (the tool being replaced)	Enterprise rollouts with managed implementation	Enterprise contracts from $30,000 a year	Visual Flow Designer	Inbound and outbound	SOC 2, HIPAA, PCI DSS, GDPR, ISO 27001
Retell AI	Visual builder plus API, pay-as-you-go	$0.07 to $0.31 per minute; $10 free credits	Drag-and-drop canvas, APIs and SDKs	Outbound batch calling and AI-to-human handoff	HIPAA, SOC 2 Type II, GDPR, ISO 27001
Bland AI	Enterprise volume with published plans	$0.14 or $0.12 per minute; $299 per month on Build	Developer access and platform	Inbound and outbound	SOC 2 Type II, HIPAA, PCI DSS v4.0
Vapi	Developers choosing their own providers	$0.05 per minute hosting plus provider costs	Developer platform, dashboard for first agents	Make and receive calls	Not reviewed
ElevenLabs (ElevenAgents)	Voice quality and language range	Free to $990 per month; extra minutes $0.080	Agent builder, APIs and SDKs	Telephony, web and more; outbound use cases	SOC 2 Type II, ISO 27001, PCI DSS Level 1; HIPAA and GDPR for enterprise deployments
VoiceOI	Outbound floors and VICIdial	$25 to $155 per bot per month, prepaid	No-code script builder (recorded-voice and LLM bots) and simulator	Outbound only, live transfer to a human closer	None published

1. Retell AI

Best for: Teams that want a visual builder and an API in one platform, with pay-as-you-go pricing

Retell describes a drag-and-drop canvas for building call flows visually, plus APIs and SDKs for programmatic control, so it lists both a visual builder and APIs. Its site also lists outbound batch calling (upload an audience, schedule campaigns, control pacing and retries) and handoffs from the AI to a human agent. Its pricing page publishes per-minute rates, which is the main contrast with the enterprise-only page we reviewed for Synthflow.

Strengths

Visual flow builder and APIs and SDKs on the same platform
Outbound batch calling with scheduling, pacing and retries, per its site
Lists integrations with Make, Twilio, Vonage and HubSpot
Lists HIPAA, SOC 2 Type II, GDPR and ISO 27001 on its site

Limits

Billed per minute, so cost rises with call volume; component costs (voice infrastructure, text-to-speech, LLM, telephony) are itemised and vary by choice
Concurrency beyond the included 20 calls is charged per month
LLM cost varies by model: its pricing page lists examples from $0.0016 to $0.32 per minute or more

Pricing: Pay-as-you-go from $0.07 to $0.31 per minute for AI voice agents, $10 in free credits, 20 free concurrent calls and $8.00 per extra concurrency per month. Enterprise is custom.

Source: Retell AI's pricing page and homepage, reviewed October 2026.

2. Bland AI

Best for: Enterprises that want inbound and outbound automation with published per-minute plans and on-premises options

Bland positions itself as an enterprise voice AI platform for inbound and outbound calls, including lead qualification and IVR replacement. Its pricing page publishes two self-serve plans and a custom enterprise plan, which makes it easier to budget than a quote-only contract. Its site lists 40+ languages, SMS and web chat on the same agent, and self-hosted or on-premises deployment for sensitive workloads.

Strengths

Published plans: a Start plan with no platform fee and a Build plan at $299 per month
LLM, speech-to-text and text-to-speech are included in the per-minute rate, with no token charges
Lists SOC 2 Type II, HIPAA and PCI DSS v4.0 on its site
Self-hosted and on-premises options for sensitive workloads, per its site

Limits

Per-minute billing, with transfer time billed at its own rate
Start plan caps at 100 calls per day and 10 concurrent calls; Build caps at 2,000 calls per day and 50 concurrent
Higher call and concurrency limits sit on the custom enterprise plan

Pricing: Start: $0.14 per minute talk time and $0.05 per minute transfer time, no platform fee. Build: $0.12 and $0.04 per minute plus $299 per month. Enterprise is custom.

Source: Bland AI's pricing page and homepage, reviewed October 2026.

3. Vapi

Best for: Developers who want to choose their own speech, language-model and voice providers

Vapi describes itself as a developer platform for building voice AI agents that make and receive phone calls, with control over each component and dozens of providers to choose from. Its docs also say you can build a first agent from the dashboard without coding. Compared with Synthflow it is more modular and more developer-oriented, and the bill is built from several parts.

Strengths

Choice of providers for transcription, language model and voice, including OpenAI, Anthropic, Google, Deepgram and ElevenLabs
A dashboard route for first agents and an API route for custom builds
A free tier with $5 in credits to try it

Limits

Hosting is only one line item: transcription, language model, voice and telephony are billed separately
Concurrency is tied to plan: 4 calls on the free tier, 10 on Core, 30 on Pro
Per its docs, outbound calling is not supported on free Vapi numbers

Pricing: $0.05 per minute Vapi hosting on the free tier, plus separately billed components: Deepgram transcription $0.0095 to $0.0099, OpenAI $0.0077 to $0.0452 and ElevenLabs voice $0.0146 to $0.0238 per minute, and Twilio outbound $0.014 per minute. Core is $29 per month and Pro is a $999 per month minimum (the page also lists 10% of Vapi hosting fees). Vapi's own example puts 1,000 minutes on the free plan at $82 to $129 a month.

Source: Vapi's pricing page and docs, reviewed October 2026.

4. ElevenLabs (ElevenAgents)

Best for: Teams that prioritise voice quality and language range and want a monthly plan with included minutes

ElevenLabs offers an agent builder, branded ElevenAgents on its current pages, where you configure voice, language, knowledge base, system prompt and workflows without engineering, along with APIs and SDKs. Its site lists Twilio as a native connector and mentions outbound use cases such as qualifying leads. Pricing is a monthly plan with included call minutes, which is a different shape from both per-minute-only and enterprise-only models.

Strengths

Plans from a free tier up to a Business plan, each with included call minutes
Says agents speak 70+ languages and can switch mid-conversation
Lists SOC 2 Type II, ISO 27001 and PCI DSS Level 1; HIPAA and GDPR available for enterprise deployments

Limits

LLM usage is billed on top, based on the model you choose
Extra call minutes cost $0.080 each and exceeding concurrency is charged at a burst rate of $0.160 per minute
Concurrency is capped by plan, from 4 to 40 concurrent calls

Pricing: Free ($0, 15 minutes), Starter $6, Creator $22 (first month $11), Pro $99, Scale $299 and Business $990 per month, with 75 to 12,375 included minutes on the paid plans. Extra minutes are $0.080. Enterprise is custom.

Source: ElevenLabs pricing page for agents, reviewed October 2026.

5. VoiceOI(our product)

Best for: Outbound call floors, especially VICIdial shops, that want per-bot pricing and fronter bots that hand qualified calls to a human closer

VoiceOI is built for outbound lead generation rather than as a general voice agent platform. A fronter bot calls a lead, asks your screening questions and, when the lead qualifies, hands the live call to a human closer over SIP with AI-written notes. In VICIdial, bots appear as remote agents and outcomes are written back; without VICIdial, a built-in dialer runs bot campaigns with lead lists, carriers, pacing and timezone windows. You build scripts yourself in a no-code builder, as recorded-voice branching bots or LLM-driven agents, and test them in a simulator. That builder is VoiceOI's counterpart to Synthflow's Flow Designer, with a narrower scope: outbound qualification rather than a general agent platform.

Strengths

Prepaid per bot, not per minute: list prices $25 to $155 per bot per month by bot type and connection, from $25 for a fronter, with volume discounts up to 60%
Runs inside VICIdial as remote agents, or over any SIP carrier, including Twilio and Telnyx SIP trunks
Answering-machine detection ends the call and logs it as AM, so bots do not talk to voicemail greetings
Google Sheets export on the Pro lead-generation tiers: one row per call with the data your script captured
Compliance controls: do-not-call phrase handling ends the call, optional TCPA AI-voice disclosure, timezone windows, recordings and transcripts

Limits

No public API and no CRM integrations yet (coming soon)
Outbound only: not an inbound receptionist, no SMS, no calendar booking and no voicemail drop
Conversations are English-first, not multilingual, and VoiceOI does not publish HIPAA, SOC 2 or GDPR certifications
Lead-generation (generative AI) tiers do not live-transfer; fronter and closer bots do

Pricing: $25 to $155 per bot per month at list price, billed prepaid per bot with no per-minute AI fee. Worked example: 10 bots on SIP Simple Fronter at $45 list is $450 per month, or $382.50 with the 15% discount that applies at 10 or more bots. Your carrier bills its own call minutes. See the pricing page for each tier.

Source: VoiceOI pricing, reviewed October 2026.

How to Choose a Synthflow Alternative

Start with the call type. If you need inbound handling, SMS or calendar booking, VoiceOI is not the right choice; Retell, Bland, Vapi and ElevenLabs list broader channels. If you run outbound lead qualification with human closers, VoiceOI is built for exactly that.
Match the billing model to your volume. Per-minute plans are easy to start and grow with every call; per-bot pricing is a flat monthly rate per bot. Take your monthly talk minutes and your peak concurrent calls and price both ways, then add carrier or telephony costs.
Check compliance requirements before features. If a buyer or regulator needs HIPAA, SOC 2 or similar attestations, only choose a vendor that lists them on its own site and ask for the documents. VoiceOI publishes none.
For outbound telemarketing, plan for consent. Since the FCC's February 2024 ruling, AI voices count as artificial voices under the TCPA, so calls generally need prior express written consent, and compliance remains your responsibility.
Run a pilot on your own script. Build the same screening script in two tools, call a small list and compare transcripts, transfers and cost per qualified lead before you commit.

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Synthflow Alternatives: FAQs

What is the cheapest alternative to Synthflow?

It depends on volume. Synthflow's pricing page lists enterprise contracts starting at $30,000 a year. Of the alternatives here, Vapi and Retell have low pay-as-you-go entry points, and ElevenLabs has a free tier, but all three bill by the minute, so cost rises with volume. VoiceOI bills a flat monthly rate per bot, so for a steady outbound floor the comparison is bots against minutes. Use the cost comparison page to run your own numbers.

How would VoiceOI be priced against a per-minute tool?

VoiceOI bills per bot, not per minute. 10 SIP Simple Fronter bots are $450 a month at list price ($382.50 after the 15% discount at 10 bots). At Bland's published $0.14 per minute Start rate, $450 buys roughly 3,200 talk minutes, before telephony costs on either side. If your 10 bots would talk longer than that each month, the flat rate costs less in AI fees. Carrier minutes are billed by your own carrier.

Which Synthflow alternative works with VICIdial?

VoiceOI is built for it: bots run as VICIdial remote agents, can be provisioned in bulk and write call outcomes back to VICIdial. VoiceOI focuses on VICIdial and SIP outbound floors. We did not find VICIdial on the pages of the other vendors we reviewed, so confirm directly with them if you need it.

Which alternative is best if I need no-code?

Retell (drag-and-drop canvas), ElevenLabs (agent builder) and Vapi (dashboard route) all describe a way to start without coding, and VoiceOI has a no-code script builder with a simulator. Bland lists developer access; we did not review its builder. Try each builder on a real script before committing.

Do any of these include inbound calls, SMS or calendar booking?

Synthflow, Bland and ElevenLabs list inbound or omnichannel features on their own sites. VoiceOI does not: it is outbound only, with no SMS and no calendar booking, so a person books the appointment on the transferred call. If you need those features, pick one of the others.

Can an AI voice agent call people without consent?

For telemarketing, no. Since the FCC's February 2024 ruling, AI-generated voices count as artificial voices under the TCPA, so telemarketing calls generally need prior express written consent. Every vendor above gives you controls, but compliance stays with you, so have counsel review your lead sources. This is not legal advice.

How current is the pricing on this page?

Vendor figures were taken from each vendor's own pricing and product pages and reviewed in October 2026. Prices and plans change, so use the source link on each entry to confirm before you buy.

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VoiceOI vs Synthflow Vapi alternatives Retell AI alternatives Bland AI alternatives VICIdial voice bot Live transfer to human closers Answering machine detection TCPA and AI voice calls VoiceOI pricing Voice AI Cost Comparison Compare All Voice AI Tools

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