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Vobiz vs Retell AI: Different Layers of the Stack

Vobiz and Retell AI operate at different layers. Retell AI is an AI voice agent orchestration platform — it handles the LLM, TTS, conversation logic, and agent configuration. Vobiz is telephony infrastructure — it handles SIP trunking, phone numbers, inbound/outbound call routing, AMD, and audio streaming. They are designed to work together, not replace each other. Retell AI’s recommended setup for PSTN calling is to connect a SIP trunk from a provider like Vobiz. If you’re looking for a telephony layer for Retell AI, Vobiz is the answer. If you’re looking to replace Retell AI’s orchestration layer, that’s a different comparison.

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What each platform does

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How they work together

The integration is straightforward. Vobiz provides the SIP trunk and phone numbers; Retell AI provides the agent logic, STT, LLM, and TTS. When a call comes in or goes out, Vobiz routes it to Retell AI via SIP.
For outbound calls, Retell AI instructs Vobiz (via REST API or SIP) to place the call. Vobiz dials, runs AMD, and connects the answered call to the Retell AI agent session. See the Retell AI + Vobiz integration guide for the full setup.

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When to use Retell AI + Vobiz

Use Retell AI as your orchestration layer and Vobiz as your telephony layer when:
  • You want a managed agent dashboard with pre-built flows, testing tools, and analytics
  • You need multiple LLM and TTS provider options through one interface
  • Your team prefers a low-code/no-code way to configure agent behavior
  • You need PSTN calling in countries beyond the US and Canada (Vobiz covers 130+)
  • You need India 140-series numbers for TRAI-compliant A2P outbound calling

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When to use Vobiz alone (without Retell AI)

Vobiz’s XML call control and WebSocket audio streaming let you build voice AI agents without Retell AI as the orchestration layer. Use Vobiz directly when:
  • You want to control every layer: your own STT, LLM, TTS, and conversation logic
  • You’re integrating with an orchestration layer that isn’t Retell AI (Vapi, Pipecat, LiveKit, ElevenLabs)
  • You want to combine IVR flows (XML) with AI segments in the same call
  • You need maximum flexibility in audio codec and streaming format
Example: Vobiz XML with embedded AI stream

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Pricing comparison

When using Retell AI + Vobiz, you pay Retell AI for the agent minutes (LLM + TTS + orchestration) and Vobiz for the telephony minutes and number rental. The two costs are separate invoices.

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India support comparison

For teams building AI voice agents in India, Vobiz handles the TRAI-compliance layer (140-series numbers, DLT registration, NDNC compliance) that Retell AI doesn’t cover.

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Developer experience

Both platforms are API-first with good documentation. The key difference is scope:
  • Retell AI docs cover agent configuration, LLM prompt setup, testing, and analytics
  • Vobiz docs cover call routing, SIP trunking, number management, webhooks, and audio streaming
For the integration between them, see the Retell AI integration guide (SIP trunk import and outbound call setup) and the Retell AI dashboard integration (UI-based setup).

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Summary