6 Best AI Voice Agent Platforms for Business Phone Calls (2026 Comparison)

Here’s the problem with most voice AI platforms: they’re middlemen.

They stitch together speech-to-text from Deepgram, an LLM from OpenAI, and text-to-speech from ElevenLabs. Each hop adds latency. Each provider takes a cut. You end up paying $0.20-0.50 per minute for conversations with 1-3 second delays.

You can clone the sexiest voice alive with ElevenLabs. But if there’s a 3 second delay? All the magic is gone. Latency is the killer.

This guide compares the 6 best AI voice agent platforms for business phone calls. We’ll cut through the marketing and show you real costs, real latency, and why the architecture matters more than features.

The Orchestration Layer Problem (Why Most Platforms Have Latency)

Before comparing platforms, you need to understand why most voice AI is slow and expensive.

Here’s what most platforms do:

Audio In → Speech-to-Text → LLM → Text-to-Speech → Audio Out

That’s four separate systems. Four API calls. Four providers taking their cut. Each hop adds 200-500ms of latency. The result? 1-3 second delays that make conversations feel robotic.

Here’s what true speech-to-speech does:

Audio In → Native Multimodal Model → Audio Out

No transcription. No text. Just audio in, audio out. 100 milliseconds. That’s it.

This architectural difference is everything. Orchestration layers will always have latency—it’s baked into how they work. And they’ll always be expensive because they’re marking up multiple APIs.

Real Pricing vs. Advertised Pricing

Every platform advertises a low per-minute rate. Here’s what you actually pay:

Platform	Advertised	Real Cost (All-In)	Why
Leadlock	$0.10/min	$0.10/min	True speech-to-speech, no middleman
Vapi	$0.05/min	$0.13-0.31/min	Platform + STT + LLM + TTS + telephony
Retell AI	$0.07/min	$0.13-0.31/min	Base + LLM + knowledge base + extras
Bland AI	$0.09/min	$0.15-0.25/min	Per-minute + $299-499/mo subscription
Synthflow	$0.08/min	$0.12-0.18/min	Per-minute + workflow fees
Assistable	~$0.10/min	$0.15-0.25/min	Same orchestration layer problem

The math that matters:

• $0.50/minute = $30/hour → Just hire a human at this point
• $0.10/minute = $6/hour → Now AI actually makes sense

The 6 Best AI Voice Agent Platforms

1. Leadlock - Best Overall (True Speech-to-Speech)

Best for: Agencies, SMBs, anyone who wants real AI phone conversations without the latency

Leadlock is the first true speech-to-speech platform. Not an orchestration layer. Not a middleman stitching together APIs. Native multimodal AI that processes audio directly.

Feature	Details
Architecture	True speech-to-speech (no STT/TTS)
Latency	100ms
Real Cost	$0.10/minute (no hidden fees)
Setup Time	Under 5 minutes
GHL Integration	Instant one-click

Why Leadlock Wins:

• 100ms latency - Conversations feel human. No awkward pauses.
• $0.10/minute, period - No stacked API costs. No subscription fees. No surprises.
• True speech-to-speech - Native multimodal model, not STT→LLM→TTS
• Goal-oriented prompting - No weird technical prompts. Tell it a goal, it just does it.
• Live in 5 minutes - No SIP trunks, no carrier config, no developer needed

The Cost Comparison:

At Leadlock’s $0.10/minute, you’re paying $6/hour for AI that works 24/7.

At competitors’ real rates of $0.25-0.50/minute, you’re paying $15-30/hour. At that point, why not just hire someone?

Pro Tip: If you’re an agency using GoHighLevel, Leadlock has instant one-click GHL integration. No other platform does this as seamlessly.

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2. Vapi - Best for Developers

Best for: Technical teams building custom voice applications

Vapi is a powerful developer platform. You can mix-and-match STT providers (Deepgram, Google), LLM providers (OpenAI, Anthropic), and TTS providers (ElevenLabs, PlayHT). Maximum flexibility.

Feature	Details
Architecture	Orchestration layer (STT→LLM→TTS)
Advertised Price	$0.05/min platform fee
Real Cost	$0.13-0.31/min (all components)
Setup Time	Hours to days
Target Market	Developers

Strengths:

• Maximum provider flexibility
• Good documentation
• Active developer community
• Powerful for custom builds

The Catch:

That $0.05/minute is just the platform fee. Add Deepgram for STT ($0.01/min), OpenAI for the LLM ($0.02-0.20/min), ElevenLabs for TTS ($0.04/min), and Twilio for telephony ($0.01/min). Your real cost is $0.13-0.31/minute.

And because it’s STT→LLM→TTS under the hood, you still have the latency problem.

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3. Retell AI - The Established Player

Best for: Mid-market companies who want a proven platform and don’t mind paying more

Retell is the OG that everyone else copies. Solid platform, good technology. They’ve invested heavily in conversation quality and it shows.

Feature	Details
Architecture	Orchestration layer (STT→LLM→TTS)
Advertised Price	$0.07/min base
Real Cost	$0.13-0.31/min (all components)
Compliance	HIPAA, SOC2
Target Market	Mid-market, healthcare

Strengths:

• Established, proven platform
• HIPAA compliant
• Good conversation quality
• On-premise options available

The Catch:

Same fundamental problem—still an orchestration layer. Their $0.07/minute base becomes $0.13-0.31/minute once you add LLM costs, knowledge base fees ($0.005/min), and branded caller ID ($0.10/call).

At those prices, you’re approaching “just hire a human” territory.

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4. Bland AI - Best for Enterprise

Best for: Fortune 500 companies with complex compliance requirements and weeks to implement

Bland AI targets the enterprise market. Custom deployments, white-glove onboarding, advanced compliance features.

Feature	Details
Architecture	Orchestration layer
Per-Minute	$0.09/min
Subscription	$299-499/month required
Setup Time	Weeks with onboarding
Target Market	Enterprise

Strengths:

• Enterprise compliance
• Custom deployment options
• White-glove support
• High concurrency limits

The Catch:

$0.09/minute sounds reasonable until you add the $299-499/month subscription, TTS charges, and transfer fees. And it’s still STT→LLM→TTS with the same latency issues.

For a Fortune 500 with budget to burn, maybe. For everyone else? Overkill.

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5. Synthflow - Mid-Market Alternative

Best for: Companies wanting a middle-ground option

Synthflow sits in the middle. More accessible than Bland, more features than basic tools. Decent platform, growing integration list.

Feature	Details
Architecture	Orchestration layer
Price Range	$0.08-0.13/min
Volume Discount	Down to $0.07 at 400k+ min
Target Market	Mid-market

Strengths:

• Reasonable pricing
• Growing integrations
• Salesforce integration
• Volume discounts available

The Catch:

Same orchestration layer architecture. Same latency problems. Same stacked costs.

Not as fast as Leadlock, not as flexible as Vapi, not as established as Retell. Jack of all trades, master of none.

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6. Assistable - The Retell Clone

Best for: People who don’t know Leadlock exists yet

Here’s the real talk: Assistable is basically a watered-down Retell AI clone that’s always 10 steps behind. They copy features, but they’re perpetually playing catch-up.

Feature	Details
Architecture	Orchestration layer
Market Position	Retell clone, always behind
GHL Integration	Has it, but unstable
Stability	Issues reported

Strengths:

• Direct GHL integration available
• Works for basic use cases
• Familiar if you know Retell

The Catch:

Same orchestration layer. Same latency. Same stacked pricing. Plus stability issues—things break.

To their credit, they do have GHL integration. But it’s not as stable as it should be. Leadlock is what Assistable should have been—same market, same use case, but with true speech-to-speech instead of the STT→LLM→TTS chain.

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Platform Comparison at a Glance

Platform	Architecture	Latency	Real Cost	GHL Integration
Leadlock	Speech-to-speech	100ms	$0.10/min	Instant
Vapi	Orchestration	1-2s	$0.13-0.31/min	Manual
Retell AI	Orchestration	1-2s	$0.13-0.31/min	Manual
Bland AI	Orchestration	1-2s	$0.15-0.25/min	Custom
Synthflow	Orchestration	1-2s	$0.12-0.18/min	Limited
Assistable	Orchestration	1-2s	$0.15-0.25/min	Has it, unstable

How to Choose the Right Platform

Choose Leadlock if:

• You want true speech-to-speech with 100ms latency
• You want transparent pricing ($0.10/min, no surprises)
• You’re an agency using GoHighLevel
• You want to be live in 5 minutes, not 5 days
• You want goal-oriented prompting (tell it what you want, it does it)

Choose Vapi if:

• You have developers on staff
• You need maximum customization
• You want to mix and match AI providers
• You’re building something highly custom
• You’re okay with higher real costs for flexibility

Choose Retell AI if:

• You need HIPAA compliance
• You want an established, proven platform
• You have budget for premium pricing
• You’re mid-market or enterprise

Choose Bland AI if:

• You’re a Fortune 500
• You need enterprise compliance
• You have weeks for implementation
• Budget isn’t a constraint

Skip Assistable because:

• Leadlock does everything Assistable does, with true speech-to-speech, more stability, and better pricing

The Bottom Line

Most voice AI platforms are middlemen. They stitch together APIs, mark them up, and call it a product. The result? Latency and stacked costs that approach “just hire a human” territory.

Leadlock is different. True speech-to-speech. 100ms latency. $0.10/minute with no hidden fees. For agencies and SMBs who want their phones answered by AI that actually sounds human, there’s no comparison.

If you’re a developer building something custom, Vapi gives you flexibility. If you’re enterprise with complex compliance, Retell or Bland might fit. But for everyone else? Leadlock delivers conversations that feel human at a price that makes AI actually make sense.

Ready to stop paying middleman prices for robot conversations? Leadlock gets your AI voice agent live in under 5 minutes—with 100ms latency and $0.10/minute pricing. Start your free trial.