Using the 3CX AI Receptionist to Stop Spam and Sales Calls

I run a small property business in the UK, handling repairs and lettings. I wanted to keep cold calls about Google listings and energy deals away from the people answering our main number. We use 3CX for our phones, so I set up its AI receptionist to screen those calls. This article explains how ours works, how to set one up in 3CX, and what other companies offer if you are on a different system.

How I set ours up

The AI receptionist answers only our main published number. Direct dial numbers are untouched and still go straight to the right person, so anyone who already has a direct number reaches us exactly as before.

When someone rings the main number, they can ask for a person by name, such as "John", or for a department such as repairs or lettings, and the receptionist puts them through.

If the caller is selling Google listings or energy deals, the receptionist does not hang up on them. Instead it transfers them to a user that does not really exist, so they end up leaving a voicemail that nobody needs to act on. The benefits are simple:

• The caller gets a normal ending to the call rather than being cut off.
• Nobody's time is used.
• The messages are still there, so I can glance at them occasionally in case a genuine caller was misjudged.

Setting it up in 3CX

3CX calls this feature AI Agents, and it needs the 3CX AI Edition licence. If you are not on it, speak to your 3CX partner.

You also need your own AI provider account. 3CX supports OpenAI and, from V20 Update 10, xAI Grok. Only one provider can be active at a time. The provider bills you directly for usage, so check its current pricing, set a budget and turn on usage alerts. Do not assume a budget stops spending; it may only warn you. Enter your API key under Admin Console > Integrations > AI > Realtime API.

Before changing anything, write down where each of your numbers currently goes, in and out of hours. That is your route back if something goes wrong. Testing on a spare number first is sensible if you have one.

1. Under Knowledge Sources, add documents or text covering opening hours, holiday arrangements and anything callers commonly ask.
2. Choose Add Agent. There are three types: Receptionist for company calls, Personal Assistant for one person's calls, and Customer Service Agent for answering questions before handing over. For a main number, pick Receptionist.
3. Give it an extension number and name, then assign the DID numbers it should answer. In my case that is only the main published number.
4. Choose a voice, write a short welcome message, decide on recording and set a maximum call duration.
5. Under Call Routing, add Route by Topic rules in plain English, such as "If the caller wants to report a repair, transfer to repairs", and pick the actual destination for each.
6. Turn on Allow Extension Routing by Name so callers can ask for people by name.
7. In Spam Filter, describe the calls you get under What Counts as Spam, for example "Unsolicited calls selling Google listings or business energy deals".
8. Choose the spam action: End Call, Transfer To, Send screening summary and disconnect or Send email and disconnect.
9. In the options, set an AI unavailable destination pointing at a real person or group, so calls have somewhere else to go if the AI is unavailable.

My dead end voicemail uses the Transfer To action, pointed at an extension that nobody actually uses, with voicemail switched on. If you prefer a written record instead, the screening summary or email options do that, but they disconnect the caller.

Be careful with calls claiming to be from HMRC or a bank, as some are genuine. Take a message and ring back on a number you already trust.

Your situation may be slightly different. ask a question below ↓ and our editorial team will reply with our advice.

Other companies offering AI receptionists

3CX is not the only option. Features and prices change often, so check current details with any provider before deciding.

Built into other phone systems:

• RingCentral launched its AI Receptionist in the UK in September 2025, sold as an add-on.
• BT Business launched an AI receptionist for small firms in October 2026.
• Dialpad has AI built into its platform.
• Zoom Phone has AI Companion features. Check its current receptionist and routing capabilities before relying on it for call answering.
• Vonage offers AI Studio, which is aimed more at developers.

Standalone services sit in front of your existing number, usually by having calls forwarded to them. Fasthosts' AI Receptionist is one example, and there are specialist AI receptionist firms too.

Traditional answering services such as Moneypenny use people to answer calls and increasingly mix in AI.

The useful distinction is between a receptionist built into your phone system and a separate service you forward calls to. Built in means calls can be routed straight to extensions and you have one system to manage. A separate service can work with many existing phone systems, provided you can forward calls to it, but transfers and voicemail may be less integrated. If you are on a hosted system where the provider locks the settings, you may be limited to whatever that provider offers.

Testing and the legal basics

Ring in yourself as a genuine caller and as a salesperson. Ask for people by name and for each department. Try a withheld number, silence, background noise and a real enquiry that might sound like a sales pitch. Check what happens when someone is busy or does not answer, and that out of hours handling still works. For the first week or so, read the transcripts and adjust your rules and spam description.

Some limits to keep in mind:

• At the time of writing (V20), 3CX gives a maximum of 3 minutes per AI call. Check the current documentation.
• No filter is perfect. Some sales calls will get through and some genuine callers may be misjudged, which is why I keep the voicemails.
• Busier lines mean higher provider bills.

Tell callers they are speaking to an automated assistant; a short, friendly welcome does this without fuss. AI call handling involves personal data even without recording, so under UK GDPR identify your lawful basis, mention the AI processing in your privacy notice, check the provider's processor terms and any international transfers, and set retention rules for recordings, transcripts and voicemails.

Do not skip the free basics. Register with TPS if you are an individual subscriber, including sole traders and some partnerships, or CTPS if you are a corporate subscriber, such as a limited company or LLP. Under PECR, organisations generally must not make unsolicited live marketing calls to registered numbers unless you have specifically consented to their calls. Report persistent nuisance callers to the ICO.

Menus change between updates, so check the current 3CX documentation before you configure anything.