Voice AI Agent Development Services

Zenkoders builds voice AI agents that answer and make phone calls in a natural voice, book appointments, qualify leads and update your CRM, 24/7. Built on Twilio, Vapi, OpenAI and Claude, our agents pick up in under one second and resolve most calls without a human. Pilots go live in 4 to 6 weeks.

Trusted by Brands

Custom Voice AI Agent Development, Built Around Your Calls

A voice AI agent is software that holds a real phone conversation. It listens, understands what the caller wants, takes action in your systems and replies in a natural voice, all within about a second. We design each agent around your actual call flows: what people call about, what they need answered, what has to be booked or updated, and when a human must take over.

Every agent we deliver includes the telephony setup, conversation design, integrations, testing and a live dashboard, so you get a working phone line, not a demo.

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Inbound AI Receptionist

Answers every call in your brand voice, handles FAQs from your knowledge base and routes or books on the spot, including nights, weekends and peak hours.

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Outbound Calling Agents

Runs appointment reminders, follow-ups, lead qualification, renewals and surveys at scale, with consent tracking and do-not-call handling built in.

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Appointment Booking & Scheduling

Checks real-time availability in Google Calendar, Outlook, Calendly or your practice software, respects buffers and confirms by SMS.

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CRM & Helpdesk Integration

Creates and updates contacts, deals and tickets in HubSpot, Salesforce, Zoho or Zendesk, so every call leaves a clean record.

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Multilingual Voice Agents

Detects the caller’s language automatically and replies in English, Spanish, French and other languages without a menu.

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Call Analytics & Quality

Full transcripts, recordings, summaries, booking outcomes and escalation reasons in one dashboard to improve the agent every week.

Where Voice AI Agents Deliver the Fastest ROI

Voice AI pays back fastest wherever the phone is a revenue channel and calls are missed, repetitive or after hours. These are the use cases we see the strongest results in:

Dental & medical clinics

Law firm client intake

HVAC & home services

Real estate lead qualification

Restaurant reservations

E-commerce order status & returns

Insurance & claims first notice

Fintech & banking support

Logistics & dispatch updates

SaaS customer support lines

Stop Sending Callers to Voicemail

Every missed call is a missed booking. See a voice AI agent answer, book and escalate a real call for your business in a 30-minute demo.

Voice AI Agent Development Services We Offer

From a single AI receptionist to a multi-location contact centre, we build the voice layer, the logic and the integrations end to end.

Custom AI Agent Development

Custom Voice AI Agent Development

Purpose-built voice agents designed around your call types, scripts, compliance rules and systems, with a custom voice and tone that matches your brand.

AI Chatbot Development

AI Voice Receptionist

A 24/7 front desk that answers in under a second, books appointments, answers FAQs and transfers urgent calls with full context to your team.

AI Automation Agent Development

Outbound Voice AI Campaigns

Automated reminder, follow-up and qualification calls that run at the times your customers answer, with results written back to your CRM.

Enterprise AI Agent Solutions

IVR Replacement & Smart Call Routing

Replace “press 1 for sales” menus with natural conversation that understands intent and routes callers to the right person or workflow.

AI Agent Integration Services

HIPAA-Ready Voice AI for Healthcare

Voice agents for clinics and practices with PII redaction, encryption at rest and in transit, audit logs and no transcript storage when required.

AI Agent Consulting Services

Voice AI Consulting & Pilots

Call audits, ROI modelling and a 4 to 6 week pilot on one real call flow, so you see the numbers before committing to a full rollout.

How We Build Your Voice AI Agent

A clear six-step process takes you from your current call data to a live, monitored voice agent.

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01. Call Audit & Discovery

We review recordings, call logs and scripts to find the call types worth automating, the questions callers ask and where calls are lost today.

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02. Conversation Design

We map the dialogue: greetings, intents, follow-up questions, confirmations and the exact rules for when the agent hands over to a human.

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03. Knowledge & Integrations

We connect your knowledge base, calendar, CRM and telephony, and set up the phone numbers or SIP trunk the agent will answer.

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04. Build & Voice Tuning

We build the agent, choose and tune the voice, and optimise speech recognition for your names, products, accents and terminology.

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05. Testing & Hardening

We run hundreds of simulated and real test calls for latency, accuracy, interruptions, edge cases and failure paths before go-live.

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06. Launch, Monitor & Improve

We go live in stages, watch every call in the dashboard and improve prompts, flows and integrations weekly based on real outcomes.

AI agent App

Why Zenkoders Is the Right Voice AI Agent Development Company

We don’t just connect a voice API to a chatbot. We ship voice products to production and run them, which is why we know where calls break: slow responses, misheard names, callers who interrupt, and integrations that fail mid-booking.

Our own AIVentra receptionist answers in under one second, resolves 94% of calls without a human and holds a 99.9% uptime SLA. We bring the same architecture, testing playbook and monitoring to your agent, and you own the code, prompts and data from day one.

With 1,000+ projects delivered since 2019 for startups and enterprises across the USA, our team covers telephony, speech, LLMs, backend integrations and compliance in one place.

How Our Voice AI Agents Work: The Technical Stack

A production voice agent is a real-time pipeline. Each layer below is engineered and tested on its own, because one slow or inaccurate layer is enough to make a call feel robotic.

Hire-AI-Agent-Developers-For-Every-Business-Need
Telephony Layer

Calls arrive through Twilio, Telnyx or Vonage phone numbers, or over SIP from your existing PBX. We handle number provisioning, call routing, recording consent and warm transfers to staff, and can run in parallel with your current phone system during rollout.

Streaming recognition with Deepgram or OpenAI Whisper converts speech to text while the caller is still talking. We add custom vocabulary for your staff names, products and locations, and tune endpointing so the agent knows when the caller has finished speaking.

GPT-4o, Claude or Gemini decides what the caller needs and calls tools: check availability, create a booking, look up an order, update the CRM. Answers come from your verified knowledge base through retrieval, not from the model’s memory.

Natural voices from ElevenLabs, Cartesia or Azure Neural TTS, streamed sentence by sentence so the agent starts speaking immediately. We tune pace, tone and pronunciation to match your brand.

Natural conversation needs a reply in under a second. We stream every layer, support barge-in so callers can interrupt, cache common answers and deploy close to your callers to keep responses fast.

Confidence thresholds, topic limits and output validation stop the agent from guessing. Trigger phrases, emergencies or repeated misunderstandings pause the call, alert your team by SMS with context and transfer the caller.

HIPAA-ready mode with PII redaction, AES-256 encryption at rest, TLS 1.3 in transit, role-based access and full audit logs. Your data is never used to train public models, and recordings follow your retention policy.

Technologies We Use for Voice AI

Twilio logo

Twilio

Telnyx logo

Telnyx

Vonage logo

Vonage

SIP / WebRTC logo

SIP / WebRTC

Vapi logo

Vapi

Retell AI logo

Retell AI

LiveKit logo

LiveKit

Pipecat logo

Pipecat

Deepgram logo

Deepgram

OpenAI Whisper logo

OpenAI Whisper

ElevenLabs logo

ElevenLabs

Cartesia logo

Cartesia

Azure Speech logo

Azure Speech

OpenAI GPT-4o logo

OpenAI GPT-4o

Anthropic Claude logo

Anthropic Claude

Google Gemini logo

Google Gemini

Llama logo

Llama

HubSpot logo

HubSpot

Salesforce logo

Salesforce

Google Calendar logo

Google Calendar

Calendly logo

Calendly

Zendesk logo

Zendesk

Zapier / Make logo

Zapier / Make

AWS logo

AWS

Azure logo

Azure

Node JS logo

Node JS

Python logo

Python

MongoDB logo

MongoDB

PostgreSQL logo

PostgreSQL

Client Reviews

Frequently Asked Questions

A voice AI agent is software that holds a natural phone conversation. It converts the caller’s speech to text, uses a large language model to understand the request and take actions such as booking or updating a CRM, and replies with a lifelike synthetic voice, usually within one second.

Most projects run from $18,000 for a single-flow pilot to $30,000–$75,000 for a production agent with several call types and integrations. Enterprise, multi-location or compliance-heavy platforms range from $75,000 to $150,000+. Telephony and AI usage are billed separately at cost, typically a few cents per call minute.

A focused pilot on one call flow goes live in 4 to 6 weeks. A production agent with multiple flows and integrations usually takes 8 to 12 weeks, and enterprise rollouts 12 to 20 weeks depending on compliance and integrations.

Our agents sound natural and respond in under a second, so most callers have a normal conversation. We still recommend a short disclosure in the greeting, and in some states and industries it is legally required. We configure this to match your compliance needs.

Yes. You define the triggers, such as emergencies, complaints, requests to speak to someone or low confidence. The agent sends your team an SMS or Slack alert with the call context and transfers the caller, so the person who picks up already knows why they are calling.

We work with Twilio, Telnyx, Vonage and SIP trunks from existing PBX systems, and integrate with HubSpot, Salesforce, Zoho, Zendesk, Google Calendar, Outlook, Calendly and custom APIs or practice-management software.

We build HIPAA-ready agents with PII redaction, AES-256 encryption at rest, TLS 1.3 in transit, audit logging and optional no-transcript storage, and sign BAAs with supported providers. Compliance also depends on your own policies, so we review the setup with your compliance officer.

English, Spanish and French are standard, with automatic language detection at the start of the call. Most major languages are supported by our speech and voice providers and can be added per project.

The agent asks a clarifying question, confirms key details such as names, dates and phone numbers back to the caller, and escalates to a human if confidence stays low. Every unresolved call is flagged in the dashboard so we can improve the agent.

Yes. You own the source code, prompts, conversation design and all call data. Your data is never used to train public AI models, and we can deploy in your own cloud account if required.

Let’s Talk About Your Voice AI Agent

Tell us how your business handles calls today. We’ll show you which calls a voice AI agent can take over and what it would cost.

Get In Touch With Us!