AI phone assistant
on your own number
Answers calls, responds to questions from your website, offers open appointment slots and sends you a summary after every call. Your existing landline number stays, the setup is a fixed price, and the assistant runs in your own account.
It runs on our own number.
What changes on the phone.
The same call, two outcomes. The difference is what reaches you afterwards.
What gets set up.
Six building blocks, all taken from our own setup.
Script & knowledge base
Conversation script and knowledge base built from your website: services, opening hours, frequent questions. You approve the text before it goes live.
Voice of your choice
German voices from Cartesia or ElevenLabs, auditioned in testing first. The language model behind it is gpt-4.1-mini.
Callback note & summary
After every call a summary with the request and callback number by email, in the Plus package additionally via Telegram.
Appointment booking
In the Plus package the assistant checks open slots in Calendly and books directly. A dedicated webhook service on Cloudflare Workers runs in your account for this.
Your number stays
Your existing landline number is connected via SIP trunk, for example with easybell using Trusted IP. Your customers keep dialling the same number.
Limits built in
AI disclosure at the start of the call, call length capped at 8 minutes, hang-up after silence, no audio recording.
What running it costs.
Measured in our own operation, as of November 2026. Billing is direct with each provider, not through me. The sources are listed in the questions below.
approx. 11–13 cents per minute
Per call minute at Retell, read off our own invoice.
approx. 2 cents per call
Additional amount per call at Retell, also from our own invoice.
€0 for the webhook service
The dedicated webhook service for slot lookups and notes runs on the free plan of Cloudflare Workers.
€1.95 / month SIP line
Example easybell Business 2: no base fee for the first six months, then €1.95 per month excl. VAT. Other providers bill differently.
Worked example: around €37–43 / month
Hypothetical worked example, not a measurement: 100 calls of 3 minutes = 300 minutes × 11–13 cents (€33–39) + 100 × 2 cents (€2) + €1.95 SIP line.
No mark-up
The accounts are in your name and the invoices come straight from the provider. What you pay me for is the setup, not your minutes.
Two scopes, both at a fixed price.
The fixed price is agreed in writing after the first conversation. All amounts exclude VAT, payable on order and after acceptance. The lead time starts once the Retell account and SIP line are in place. You pay minutes and line directly to the provider (see above). If you want the assistant looked after afterwards, that is what Agent Operations is for, from €390 / month — optional, not a precondition.
Answers calls on your number, responds to questions from your website and sends a callback note by email after every call.
Everything in Basis, plus slot lookup and booking in Calendly and the note additionally via Telegram. This is how it runs at Pragma Code itself.
From your website to the phone.
The content decides what the assistant may say. That is why it comes first and the technology after.
Clarify the content
From your website and a short conversation: what do callers ask, what may the assistant say, when does it refer to a callback?
Accounts & number
You create the Retell account, I set up agent, voice and webhook and connect your number via SIP trunk.
Test calls
We call together: normal questions, an appointment request, silence, a dropped call. Then you approve the script and flow.
Live & refine
After the first real calls we go through the summaries together once and refine the script and knowledge base.
Frequently asked.
Including costs, data protection and the cases it is not meant for.
Do I need a new phone number?
What does it cost to run per month?
Does the caller know they are talking to an AI?
Is the call recorded?
What about data protection?
Which businesses is this for?
Does this work for medical practices or law firms?
Can I try it first?
What happens after the setup?
More on the topic.
Voice agents, call handling and the question of when AI on the phone holds up.
AI Phone Reception & Call Handling
How pipelines of speech recognition, language model and voice carry a phone call.
Read more
AI Chatbots & Voice Agents
When a language model holds up in support — and when rules are enough.
Read more
EU AI Act for SMEs
What the AI Act requires of deployed AI workflows, step by step.
Read moreBuilding the agent is the quick part. Staying reliable is not automatic.
Models get deprecated, fallbacks kick in silently, prompts lose their effect — and unlike a workflow, an agent does not stop when that happens; it keeps answering. The Agent Operations product line takes over monitoring, the monthly quality sample against a fixed test-case set and, on request, the AI Act documentation. From €390 / month, cancel monthly.
Who answers your phone when nobody is free?
In 20 minutes we clarify how your number can be connected, which questions the assistant should take on and which package fits.