AI receptionist guide

Set up your AI receptionist in about 30 minutes.

How to get a number, connect Retell to your CRM and go live. And exactly what 100 minutes of calls will cost you.

See the costs

Your AI receptionist answers every call in your business name, in British English, day and night. It answers questions from your own information, takes the caller's details, and puts everything into the CRM: the call, the transcript, a new contact, and a follow-up text and email. It runs on Retell, on your own Retell account, so you only pay Retell for the minutes you use.

What you need (about 30 minutes)

  • A card for a Retell account (Retell gives you $10 of free credit to test with).
  • A phone number for the receptionist. You can buy one in Retell, bring one you already have on Twilio, or simply forward your existing business number to it.
  • Your opening hours, prices, services and your top 10 questions written down.

Step 1: Create your Retell account and API key

  1. Go to retellai.com and sign up. Add your card under Billing.
  2. Open Settings, then API Keys.
  3. Copy the key that has the webhook badge next to it. Retell uses that key to sign the call reports it sends to the CRM, so it must be this one.

Step 2: Create the agent

  1. In Retell, open Agents and click Create an agent.
  2. Choose Single Prompt. The CRM can only write its instructions into this type.
  3. Pick a British voice. Try two or three and ring yourself to hear them properly: the preview is smoother than a real call.
  4. Set the language to English (UK) and choose the AI model. GPT 5.6 Terra or Claude 5 Sonnet give the best balance of quality and cost.
  5. Save the agent and copy its Agent ID (shown under the agent's name).

You do not need to write the instructions or set a webhook. The CRM does both for you in step 4.

Step 3: Get a phone number

Pick the option that suits you.

A. Keep your number and forward it (easiest)

Buy or import a number in Retell (option B or C), then set up call forwarding on your existing business line to that number. Most landline and mobile providers let you forward all calls, or only when you are busy or do not answer. Your customers keep ringing the number they already know.

B. Buy a number in Retell

In Retell open Phone Numbers, click Buy number and choose the United Kingdom. UK numbers need a one-off regulatory check (photo ID, proof of a UK business address from the last 12 months, and your company details), so allow a few working days. About £1.50 a month.

C. Bring a Twilio number you already have

In Twilio, create an Elastic SIP Trunk, point its origination at Retell and add your number to it. Then in Retell open Phone Numbers, choose Import and enter the number and your trunk details. Retell's guide "Connect Retell to Twilio with elastic SIP trunking" walks through each screen. Retell does not charge phone line fees for imported numbers; Twilio bills you instead.

Once the number is in Retell, open it and set Inbound call agent to the agent from step 2.

Step 4: Connect it to the CRM

  1. Open the AI Receptionist page in the CRM. You need to be an admin.
  2. Open Connection details and paste your Retell API key, Agent ID and phone number (in full, for example +441234567890). Click Save and check.
  3. Fill in the greeting, tone and knowledge base further down the page, then save.
  4. Click Update and publish agent. The CRM writes your instructions into Retell, points the call reports at the CRM, sets up what to capture after each call, and publishes the agent.
  5. The status line should show: calls report to the CRM, and your number is answered by this agent.

Whenever you change your knowledge base or greeting and save, the CRM updates Retell for you.

Step 5: Test it

  1. Ring the number from your mobile. It should answer within two rings.
  2. Ask something that is in your knowledge base, such as your opening hours. Check the answer.
  3. Ask something that is not, such as a service you do not offer. It should offer to take your details, not make something up.
  4. Leave your name and email. Within a minute the call appears in the CRM with a transcript, you appear as a contact, and your follow-up text is queued.

What it costs

You pay Retell directly for the minutes your receptionist is on the phone, billed to the second. There is no monthly platform fee. The price per minute depends on the voice and AI model you choose, plus the UK phone line.

Set-upWhat it usesPer minute100 minutes250 minutes500 minutes
BudgetRetell platform voice + GPT 5.4 mini8.3p£8.28£20.71£41.42
RecommendedElevenLabs voice + GPT 5.6 Terra or Claude 5 Sonnet13.2p£13.22£33.06£66.12
PremiumElevenLabs voice + GPT 5.520.5p£20.52£51.30£102.60

Plus about £1.50 a month for a phone number bought in Retell.

What 100 minutes looks like

Most receptionist calls last 2 to 3 minutes, so 100 minutes is roughly 35 to 50 calls. On the recommended set-up that is about £13.22, or around 30 to 40p a call, plus the number. A business taking 10 calls a day would use about 500 to 700 minutes a month, which is roughly £66.12 to £92.57.

Prices are Retell's published pay-as-you-go rates in US dollars (voice platform $0.055, voice $0.015 to $0.04, AI model $0.024 to $0.16, UK line $0.015 per minute), converted at about 76p to the dollar, checked on 27 September 2026. Your bank's exchange rate, VAT and optional extras (such as advanced noise removal at $0.005 a minute) can change the final figure. Retell charges for the whole connected call, including silences. For the latest prices see retellai.com/pricing.

Common problems

The status says Retell did not accept the API key
Copy the key again from Settings, API Keys. Make sure it is the one with the webhook badge.
"This agent does not use a Retell LLM"
The agent was created as a conversation flow. Create a new agent and choose Single Prompt.
The number is "not linked to this agent in Retell yet"
In Retell, open the phone number and set its inbound call agent to your agent.
Calls work but nothing appears in the CRM
Click Update and publish agent again. That resets the call report address. Check you used the webhook key.
Calls cut off mid-sentence
Your Retell balance has run out. Top up or turn on auto-recharge in Retell's billing page.
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