Build AI voice agents that actually talk to your customers
Nixflex is the voice AI platform that runs its own engine — so you get real-time phone calls, web calls, SMS, appointments and transfers through one API, on your own carrier, for a flat $0.08 a minute.
Why teams choose Nixflex
Most voice tools are an orchestration layer — they wire a speech vendor, a model, and a telephony provider together and hand you the bill for all three. Nixflex is built as a modern alternative: one engine, one API, one flat price. Here is what that gets you.
We run the voice pipeline ourselves. That is why we can offer Live Monitor — listen to a live AI call in real time — which glued-together platforms cannot.
One transparent rate, not a base fee plus separate speech, model and carrier charges you reconcile across vendors. The premium model is included, not billed on top.
Connect your own Twilio or Telnyx account. You keep control of your numbers and your call and number costs stay on your own carrier bill.
Create agents, attach numbers, run campaigns and manage SMS entirely in code — and put an agent behind every one of your own customers from day one.
The same number answers calls and replies to texts automatically. No separate chatbot to build or bill.
Write a prompt, attach a number, and the agent is answering — no flow-builder to wire up. Businesses set it up in the dashboard in about five minutes.
Comparing options? Nixflex is built as a modern alternative to Retell, Vapi and Bland. See how they stack up →
What a voice AI platform actually does
A voice AI platform turns a phone number into an agent that holds a real conversation. It listens, understands what the caller means, and speaks back in a natural voice — fast enough for a genuine back-and-forth. The difference from a traditional phone menu is not a nicer voice; it is that the caller no longer bends to the machine. Someone can say "I need to push my Tuesday appointment to later in the week" and the agent works out the intent, checks real availability, books it, and confirms — without a single menu tree.
For developers, that capability arrives as one REST API: create an agent with a prompt, attach a number, and it answers calls and texts. For businesses, the same thing is a dashboard you configure in about five minutes. Nixflex is built for both.
One engine, not a stack of vendors glued together
Most voice tools stitch a speech provider, a language model, and a telephony vendor into a pipeline. Every hop adds latency and a new place for a call to fail — and when something breaks, you are debugging across three companies. Nixflex runs its own engine. The speech-to-text, the reasoning, and the voice all move through infrastructure we operate, which is why we can offer things closed platforms cannot.
Live Monitor
Listen to a live AI call in real time from a phone or tablet. Because we run the engine, we can tap the audio — glued-together platforms cannot easily do this.
One number, voice + SMS
The same number is a call agent and a chat agent. When someone texts, your AI replies automatically — no separate bot to build.
Tag-based actions
The agent triggers transfers, SMS, and call endings through prompt tags. No webhook orchestration needed for built-in actions.
History-aware calls
Outbound calls pull past call summaries for that person and inject them into the prompt. Your agent remembers customers across calls.
How a call moves through the engine
- The call connects. A caller dials your number, or you trigger an outbound call through the API.
- Audio streams in. Your carrier streams the call to Nixflex over a live connection.
- Speech becomes text. The engine transcribes what the caller says as they say it.
- The agent reasons. It decides what to say or do next — answer, transfer, book, send a text, call your API.
- Text becomes voice. The reply is spoken back in a natural voice and streamed to the caller.
- The call is analysed. Afterwards, Nixflex writes a summary, scores sentiment, extracts data, and fires your webhook.
Everything a phone agent needs, built in
Connects to the tools you already run
Integrations are configured per phone number, so each agent connects to the right calendar, CRM, and automation. Book with Cal.com or Google Calendar live during a call, log every conversation to GoHighLevel, post summaries to Slack, or push call data into Zapier and Make to automate the rest.
Simple, flat pricing
Pay only for what you use. Voice is $0.08 per minute. Numbers with Live Monitor enabled bill inbound minutes at $0.09. SMS is billed per message at your carrier rate. No platform subscription to get started, and because you bring your own carrier, your call and number costs stay on your own Twilio or Telnyx account.
Create your accountBuilt for developers and for businesses
Everything is one REST API. Create an agent with a prompt, attach a number, and it answers calls and texts. Call your own APIs mid-conversation with custom functions, receive every call as a webhook, and manage agents, numbers, campaigns and SMS entirely in code. Multi-tenant from day one, so you can put a voice agent behind every one of your own customers.
Read the quickstart →No code required. Set up an agent in the dashboard in about five minutes: write how it should greet callers and what it should do, connect your calendar, and point your number at it. It answers every call, books appointments, sends confirmations by text, and hands off to a person when it needs to.
Set it up in the dashboard →What you can build on it
One platform covers the calls a business actually makes and receives. A few of the most common:
A receptionist that never misses a call
Answers every inbound call, tells callers what they need, books them in, and transfers to a human when it should.
Outbound calling at scale
Launch a batch campaign that calls a whole list, detects voicemail, leaves the right message, and reports back.
A booking line
The agent checks real calendar availability and books, reschedules or cancels live on the call, then texts a confirmation.
A support line wired to your systems
Custom functions let the agent look up an order, check an account, or trigger an action in your own software mid-call.
Frequently asked questions
What is a voice AI platform?
A voice AI platform turns a phone number into an AI agent that can hold a real conversation — it listens, understands open-ended requests, and speaks back naturally. Unlike an old IVR phone menu, it does not trap callers in "press 1 for sales." A caller can say "move my appointment to Friday afternoon" and the agent checks the calendar, books it, and confirms — in plain language.
How is Nixflex different from other voice AI platforms?
Nixflex runs its own voice engine rather than stitching together separate speech, model, and telephony vendors. Because the engine is ours, we can do things closed or glued-together platforms cannot — like Live Monitor, which lets you listen to a live AI call in real time from your phone. It also means one flat price and one API instead of several bills and several dashboards.
Do I need my own phone number?
Yes — you bring your own Twilio or Telnyx number and connect it. You keep full control of your numbers and carrier billing, and Nixflex is multi-tenant from day one, so each customer can connect their own carrier account.
What can the agent actually do on a call?
Answer inbound calls and place outbound ones, transfer to a human (cold or warm), send SMS mid-call or after, book and reschedule appointments live, run post-call analysis, and call your own APIs mid-conversation through custom functions. The same number is also a chat agent — when someone texts it, the AI replies automatically.
How much does it cost?
Pay-as-you-go at $0.08 per minute of voice. Numbers with Live Monitor enabled bill inbound minutes at $0.09. SMS is billed per message at your carrier rate. No monthly platform fee to start.
Is it for developers or for businesses?
Both. Developers embed voice agents into their SaaS through one REST API. Businesses that just want a phone agent can set everything up in the dashboard in about five minutes — no code.
Put a voice agent on your number today
Create an agent with one API call, or set it up in the dashboard in five minutes.