An AI Calling Agent that automated 78% of inbound loan qualification calls.
A US-based consumer lender was losing qualified borrowers to a 6-hour callback window. We shipped a multilingual voice agent on Twilio + GPT-4o Realtime that answers in 12 seconds, qualifies in 3 minutes, and books a human follow-up — 24/7.
The challenge
A 6-hour callback window was killing conversion.
Inbound leads spiked at night and weekends — exactly when the human team was offline. Conversion dropped 47% on after-hours leads. Hiring a 24/7 call center quoted at $480K/year before a single loan was booked.
The solution
A real-time voice agent with safe human handoff.
We designed a bilingual agent that picks up in under 12 seconds, runs a 14-intent qualification flow, books a follow-up in Calendly, and warm-transfers complex cases to on-call humans with full context preloaded.
Tech stack
What we built it on.
- Twilio Programmable Voice
- LiveKit Agents
- Deepgram Nova-3 STT
- ElevenLabs Turbo v2.5
- OpenAI GPT-4o Realtime
- LangGraph state machine
- Function calling
- Guardrails AI
- Pinecone vector store
- Postgres + pgvector
- Redis short-term memory
- Node.js + Fastify
- HubSpot CRM
- Calendly API
- Twilio SMS fallback
- Langfuse traces
- Sentry
- Grafana + Loki
- Custom QA dashboard
Timeline
8 weeks from kickoff to 100% production traffic.
- Week 1Discovery & Call Audit
Listened to 200+ recorded calls, mapped 14 intents, defined success metrics with the ops team.
- Week 2Conversation Design
Built dialog flows in LangGraph, wrote persona + guardrail prompts, scripted 60 edge cases.
- Week 3–4Voice Pipeline MVP
Wired Twilio ↔ LiveKit ↔ GPT-4o Realtime. Hit sub-800ms turn latency.
- Week 5CRM & Calendar Integration
Two-way HubSpot sync, Calendly booking, SMS fallback for failed transfers.
- Week 6Shadow Mode Pilot
Ran in parallel with human agents on 1,400 calls. QA dashboard caught 31 prompt regressions.
- Week 7Tuning & Localization
Added Spanish + Hindi voices, tuned barge-in handling, deployed regional accent models.
- Week 8Production Rollout
Phased traffic ramp 10% → 100% with automatic human handoff for complex cases.
Results after 90 days
Hard numbers, not vibes.
- 78% of inbound calls fully resolved by the agent — zero human touch.
- Average answer time: 12 seconds, down from 6 hours.
- 4.2× more qualified demos booked, with 92% show-up rate.
- −71% cost per qualified call vs. outsourced call center quote.
- CSAT 4.6 / 5 across 3,800 surveyed callers.
Deliverables
What shipped.
- Production-ready bilingual voice agent (EN/ES/HI)
- LangGraph orchestration with 14 intents + safe handoff
- HubSpot + Calendly + Twilio SMS integrations
- QA dashboard with call replay and prompt regression tests
- On-call playbook and 30-day support retainer
"It's the cheapest, most patient SDR we've ever hired — and it never sleeps. The thing paid for itself in week three."
Explore more work
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