1. VoiceOI(our product)
Best for: outbound call floors, especially VICIdial shops, that want per-bot pricing
VoiceOI runs AI fronter bots that call a lead list, qualify each lead with a short script and hand qualified calls to a human closer. It is built for outbound lead-generation and telemarketing floors rather than as a general voice agent platform. Bots can run inside VICIdial as remote agents, or through VoiceOI's own built-in dialer for bot campaigns.
Strengths
- Bots appear in VICIdial as remote agents, can be provisioned in bulk, and write outcomes back to VICIdial.
- Live transfer: the bot hands the live call to your human closer over SIP, with AI-written call notes.
- No-code script builder for recorded-voice bots and LLM-driven AI agents, plus a simulator, call recordings and transcripts.
- Any SIP carrier works, including Twilio and Telnyx SIP trunks, added by pasting a carrier config block.
- Answering machine detection ends the call and logs it as AM; spoken do-not-call phrases end the call; an optional TCPA AI-voice disclosure is available.
- Measured turns of about a second in testing.
Limits
- Outbound only: no inbound receptionist or general inbound IVR.
- English-first; conversations in other languages are not offered.
- No native CRM integrations yet (coming soon). Google Sheets export is available on the Pro LG tiers.
- No free plan.
- Does not leave voicemail messages: the call ends when a machine is detected.
- Lead-gen (LG) tiers do not include live transfers; fronter and closer bots do.
Pricing: Prepaid per bot, one concurrent call slot each: $25-$155 per bot per month by bot type and connection (fronter bots from $25, lead-gen bots from $50, closer bots from $100), volume discounts up to 60%, and no per-minute AI fee. Your carrier bills carrier minutes.
Source: VoiceOI pricing page, reviewed October 2026.
2. Retell AI
Best for: teams that want a visual builder and pay-as-you-go pricing for inbound and outbound calls
Retell AI describes itself as an "AI Voice Agent Platform for Phone Call Automation". Its homepage lists receptionist, appointment setting, lead qualification and customer service use cases, batch outbound calls, a drag-and-drop canvas, SIP trunking, and human takeover of a live call. Feature details per https://www.retellai.com/.
Strengths
- Pay as you go with no annual contract; $10 in free credits at sign-up.
- Twenty concurrent calls are included, with more available at $8 per concurrency per month.
- Its homepage lists integrations including HubSpot, Go High Level, Make and n8n.
- Its homepage states HIPAA, SOC2 Type II, GDPR and ISO 27001 compliance.
Limits
- The $0.07-$0.31 per minute range combines voice infrastructure, text-to-speech and LLM costs, so the final figure depends on the LLM and voice you pick; add-ons are extra.
- US telephony via Twilio is listed separately at $0.015/min; its page says there is no charge for SIP trunking or custom telephony.
- Check their site for answering machine detection and VICIdial support.
Pricing: Pay as you go: $0.07-$0.31 per minute for voice agents, a combined figure that already includes voice infrastructure ($0.055/min), text-to-speech and LLM costs. Add-ons such as advanced denoising and safety guardrails are +$0.005/min each. US telephony via Twilio $0.015/min; no charge for SIP trunking or custom telephony. $10 in free credits; Enterprise is custom.
Source: Retell AI pricing page, reviewed October 2026.
3. Vapi
Best for: developers who want to pick their own speech, LLM and voice providers
Vapi's homepage describes a platform to "Build, deploy, and improve voice agents", aimed at builders: developers and enterprises. It describes an API-native design with 30+ integration logos, and its pricing page itemizes each part of a call. Feature details per https://vapi.ai/.
Strengths
- Itemized pricing: you see the hosting fee, speech, LLM and voice costs separately.
- Its pricing page lists Vapi telephony/SIP and WebSockets as free, with Twilio, Vonage and Telnyx rates shown.
- Starts with 4 concurrent calls and $5 in free credits; Core is $29/month for 10 concurrent calls.
- Testing and simulation are included.
Limits
- The $0.05/min hosting fee is only one part of the bill; speech, LLM and voice are billed separately, so the all-in rate depends on your provider choices.
- Pro has a $999/month minimum for 30 concurrent calls.
- Check their site for a no-code builder, transfer, answering machine detection and VICIdial support.
Pricing: $0.05/min hosting fee plus provider costs billed separately. Example ranges on its page: transcription $0.0095-$0.0099/min, LLM $0.0077-$0.0452/min, voice $0.0146-$0.0238/min. Optional Core $29/month; Pro $999/month minimum.
Source: Vapi pricing page, reviewed October 2026.
4. Synthflow
Best for: enterprises that want a vendor-managed rollout with many integrations
Synthflow describes itself as an end-to-end voice AI platform with in-house telephony for enterprise customers, including BPO and call center teams. Its homepage lists inbound and outbound automation, a Visual Flow Designer, voicemail detection, human handoff, SIP integration and 200+ integrations. Feature details per https://synthflow.ai/.
Strengths
- Implementation, onboarding, testing, training and launch support are part of its enterprise package.
- Its pricing page lists CRM, calendar, contact-center, webhook and API integrations.
- Telephony options include its native telephony, SIP trunking or approved enterprise telephony.
Limits
- Its pricing page lists a single Enterprise plan with contracts starting at $30,000 a year, scoped on volume, concurrency, telephony, integrations, security and launch support.
- Check their site for VICIdial support and language coverage beyond the English and Spanish in its case studies.
Pricing: Enterprise contracts start at $30,000 annually; final pricing is scoped to your volume and setup.
Source: Synthflow pricing page, reviewed October 2026.
5. Telnyx Voice AI Agents
Best for: developers who want the AI agent and the carrier on one invoice
Telnyx is a carrier, and its Voice AI Agents product page lists a single $0.05/min rate covering orchestration, speech-to-text and text-to-speech, 80+ languages, 1,400+ voices, 30+ pre-built integrations, call transfer as a built-in tool and an AI Assistant Builder, a no-code interface. It targets developers and enterprises building voice applications. Feature details per https://telnyx.com/products/voice-ai-agents.
Strengths
- One Telnyx invoice covers the AI engine and the telephony.
- Its pricing page lists 500 concurrent calls on pay-as-you-go.
- SIP trunking rates are published (from $0.005/min outbound).
- Telnyx also works as a SIP carrier for VoiceOI bots.
Limits
- The $0.05/min engine rate excludes the LLM (billed per token) and telephony (carrier cost from $0.0032/min inbound; outbound SIP trunking from $0.005/min).
- Check their site for answering machine detection and VICIdial support.
Pricing: $0.05 per minute for orchestration, speech-to-text and text-to-speech; LLM billed per token; telephony add-on with carrier cost from $0.0032/min inbound and outbound SIP trunking from $0.005/min.
Source: Telnyx Voice AI Agents pricing page, reviewed October 2026.
6. ElevenLabs Agents
Best for: teams that want a large voice library and many languages
ElevenLabs Agents are described as "conversational agents that feel human" across voice, chat and email. Its agents page lists 70+ languages, 16,000 voices, inbound support and outbound at scale, and integrations including Zapier, Salesforce, HubSpot and Twilio. Feature details per https://elevenlabs.io/agents.
Strengths
- A free plan with 15 minutes and 4 concurrent calls lets you try an agent before paying.
- Published plans from $6 to $990 a month, with included minutes and concurrency per plan.
- Its page says agents can switch between languages mid-conversation.
Limits
- Standard calls are $0.08/min (burst $0.16/min) with LLM costs billed on top by usage and model.
- Its pricing page says telephony is billed by external providers directly rather than by ElevenLabs.
- Check their site for call transfer, answering machine detection, SIP and VICIdial support.
Pricing: Standard call rate $0.08/min; plans: Free $0, Starter $6, Creator $22, Pro $99, Scale $299, Business $990 per month, Enterprise custom. LLM costs extra.
Source: ElevenLabs Agents pricing page, reviewed October 2026.
7. Thoughtly
Best for: teams that want voice, SMS and email follow-up on inbound leads
Thoughtly's homepage says its agents respond to leads in seconds, qualify them and book meetings. Its pricing page lists voice, SMS, email and workflows on all plans, 34+ languages with voice cloning, inbound and outbound agents, 200+ integrations plus a REST API, and two-way CRM sync with HubSpot, Salesforce and Zoho. Feature details per https://www.thoughtly.com/.
Strengths
- Voice, SMS, email and workflows are included in every plan, with no per-channel fees or per-seat charges, per its pricing page.
- Two-way CRM sync and a REST API are listed on every plan.
- Its homepage says every interaction is logged to your CRM, so your team has full context when they step in.
- Scale and Enterprise add auto-QA and evaluations.
Limits
- Per-minute rates are not stated on its pricing page; Flex starts at $500 per month, usage above plan allowances is billed in arrears, and Scale and Enterprise are tailored.
- Check their site for SIP, answering machine detection, a no-code builder and VICIdial support.
Pricing: Flex starts at $500 per month; Scale and Enterprise are tailored quotes. Its pricing page says voice, SMS, email and workflows are included in every plan, with no per-channel fees. Per-minute rates are not stated.
Source: Thoughtly pricing page, reviewed October 2026.