Retell AI Alternative: PBX-Native Voice AI With Extension Registration
Retell AI has solid SIP trunking and multi-LLM support, but lacks PBX extension registration and engineering support. VoiceInfra registers AI agents directly as PBX extensions - one platform, one relationship, no external dependencies.
VoiceInfra vs Retell AI: Feature-by-Feature
A transparent comparison so you can make the right choice for your business.
Solid SIP Trunking With Strong Multi-LLM Support
Retell AI offers SIP trunking on all plans (free if you BYO carrier), multi-LLM support (GPT-5, Claude 4.6, Gemini 3.0, plus BYO-LLM via WebSocket), a visual no-code builder, and chat/callback widgets. For straightforward SIP use cases, it works well - but be aware that the advertised $0.055/min voice rate stacks up to $0.13-$0.31/min with LLM and telephony add-ons.
No PBX Extension Registration, Opaque All-In Pricing
No PBX extension registration - SIP trunking is available, but PBX-native features are absent. No engineering support services. Standard plan support is Discord and email only. The true all-in cost with LLM and telephony add-ons can reach $0.31/min - significantly higher than the $0.055/min advertised voice rate.
Why Teams Choose VoiceInfra Over Retell AI
VoiceInfra is built from the ground up for telecom operators, MSPs, and contact centers who need deep PBX integration.
Direct PBX Connection
VoiceInfra connects directly to your PBX. No third-party SIP partners, no extra vendor management. One platform, one relationship.
Simple, Predictable Pricing
Subscription plans with included minutes and transparent overage rates. No hidden LLM markups, no telephony add-on surprises.
Engineering Support Included
Direct engineering support for the integrations Retell requires a partner for - and it's included in your plan. No extra fees for complex PBX setups.
Retell AI is a strong platform for standard SIP use cases. Choose VoiceInfra if you need deep PBX integration with extension registration - and want engineering support included, not extra.
Contact SalesReady to switch?
See why businesses are choosing VoiceInfra over Retell AI. Contact our sales team for a platform walkthrough and see exactly how VoiceInfra handles what Retell AI cannot.