You connect an AI voice agent to your existing phone system in one of three ways: forward calls to it, give it a SIP line from your PBX, or point a number at it directly. Forwarding is fastest, a SIP connection is the most flexible, and either way the agent must hand calls to a person cleanly when needed.
Why the phone system is the part people worry about
Most businesses already have a phone setup they depend on: a cloud phone service, an office PBX, a mobile number printed on every van. The reasonable fear is that adding an AI agent means ripping that out. It does not. A well-planned AI voice agent sits alongside your current system and takes the calls you choose to send it. You keep your numbers, your handsets and your staff routines.
The work is in the plumbing: how a call reaches the agent, what happens when a person should take over, and how the result gets written down. Our post on how AI voice agents work covers the conversation itself. This one covers the connection.
Three ways to connect an AI voice agent
Call forwarding to the agent
The simplest option. Your phone system forwards calls to a number the agent answers. You can forward everything, only after hours, or only when nobody picks up within a few rings or the line is busy. This needs almost no change to your existing setup, which makes it a good way to start. The limitation is that the agent sees less about the original call, such as which line or department it was meant for, unless your system passes that information along.
SIP trunk or extension on your PBX
If you run a PBX, the agent can connect as an extension or through a SIP trunk. SIP is the standard way phone systems talk over the internet. This gives you more control: the agent can sit inside your call flow, receive calls from a menu choice, and transfer them back to specific extensions or queues. It takes more setup and someone who knows your PBX, but it is the cleanest option for businesses with several departments.
A dedicated or ported number
You can also point a number straight at the agent, either a new one for a campaign or an existing one moved over. This suits businesses that want the agent to be the front door, for example a service line where every call starts with booking or triage. It is a bigger change than forwarding, so we usually suggest proving the agent on forwarded calls first.
Not sure which connection fits your phone setup?
Tell us what system you use and when you miss calls. We will tell you which route is simplest and whether your setup needs any change at all.
Book a Free Call-Flow ReviewHanding the call to a person
Cold transfer and warm transfer
A cold transfer passes the call across and hangs up. A warm transfer has the agent stay on the line, tell the staff member who is calling and why, then step away. Warm transfers are friendlier because the caller does not have to repeat themselves, but they need your phone system to support them. Decide which you need before you choose a connection method, because it affects the choice.
What happens when nobody answers
Design the unhappy path first. If the agent transfers a call and the receiving line is busy or unanswered, the agent should come back, take a message, offer a callback or book a slot. A call that drops into silence is worse than no agent at all. This is also why the agent should never be the only route to a human for urgent matters; give emergencies a direct path.
Caller ID and identifying the business
Callers should see a number they recognise. Check how your provider handles caller ID on outbound calls and callbacks, and make sure the agent identifies the business clearly at the start of every call.
What should happen after the call
A call that ends with nothing recorded is wasted. At minimum the agent should leave a summary, the caller details and the outcome somewhere your team already works. For many of our customers that means a CRM, and for Odoo users it means writing the lead or booking straight into the system, as described on our Odoo AI CRM page. Decide what a successful call produces, and make sure a human can see it before the next working day starts.
Recording, consent and data
Recording and consent rules differ by country and sometimes by state, and they apply to AI calls as they do to human ones. Ask your own adviser what applies in your markets, and tell callers clearly at the start of the call that they are speaking with an automated assistant and that the call may be recorded if it is. If voice data has to stay inside your own network, an on-premise deployment is possible.
Capacity, reliability and fallbacks
Ask what happens if the agent or the internet connection is unavailable. A good setup falls back to your normal routing, such as ringing a mobile or going to voicemail, so a fault never leaves callers with a dead line. Also check how many calls the agent can hold at once, which is the reason many businesses add it; we explain this in AI agent call capacity, and the wider question of whether callers accept it in can AI answer business calls.
Questions to ask your phone provider first
Before any project starts, a short conversation with whoever supports your phone system saves weeks. Ask whether your plan allows forwarding to an external number and whether forwarding can depend on busy or no-answer conditions. Ask whether it supports SIP connections or extensions for third parties, and whether there are limits on how many calls can be forwarded at once. Ask how a transfer back to your team would work and whether the original caller number is passed along. Finally, ask how calls are recorded today and where recordings are stored, since the agent adds to that picture rather than replacing it.
These answers decide the connection method more than any technical preference of ours. Some cloud phone services make SIP trivial, while some older office systems only offer simple forwarding. Both work. What matters is choosing the approach that suits what you have, rather than changing your phones to suit the agent.
What good looks like after the first month
You should see fewer missed calls, a short daily summary of what the agent handled, and a clear list of calls it passed to a person with the reason. You should also be able to point to the calls it handled badly and see them fixed. If you cannot read what happened on a call, the setup is not finished. Our post on missed calls and what they cost explains why this is worth the effort.
A sensible way to roll it out
Start with after-hours or overflow calls only, where the alternative is voicemail and the risk is low. Listen to real calls for a couple of weeks and fix what you hear. Then widen to busy periods, then to specific call types. Keep the old routing as a one-step switch back. Because the work is mostly about your phone system, custom development is sometimes needed for unusual PBX setups or CRM links, and we will say so plainly after looking at your configuration.