Retell agents on Voice Logica

Your Retell agent answers your number through Voice Logica, calls out from it, and transfers callers to your team, blind or warm. Every call is recorded in Voice Logica and can be analysed next to your team’s calls.

Being rolled out

If you don’t see Connect an AI agent (ElevenLabs, Vapi, Retell) on your line, ask us in Support and we set it up for you.

Before you start

• Your own line in Telephony: a SIP trunk from your own carrier or your office PBX. Voice Logica’s own numbers can’t carry an outside agent.
• Your agent in Retell.
• Trunk minutes on your plan (see What is charged).

A Retell API key is optional. With a key, Connect sets up the Retell side in one click. Without one, you copy a few values into Retell yourself (Set it up without an API key).

1. Send your number’s calls to the agent

1. Open the line

   Telephony - Trunks, open the line that has your number.

2. Choose the destination

   Under Default Inbound Destination, set Destination Type to SIP URI (AI platform or SIP system) and pick the Retell preset.

3. Connect the agent

   With an API key: in AI agent on this line, click Connect an AI agent (ElevenLabs, Vapi, Retell), choose Retell, paste your key if none is saved yet, pick the Agent and click Connect.

   Without a key: follow Set it up without an API key below.

4. Call your number

   Your Retell agent answers. The call appears in Calls.

Connect does the Retell side for you: it imports your number in Retell with this line’s address and a login only Retell uses, and assigns your agent. The same number in Retell is now set up to call out through your Voice Logica line too (section 3). The key is in Retell dashboard - Settings - API Keys.

Set it up without an API key

1. Open Set it up by hand

   On the line, in AI agent on this line, open Set it up by hand. It shows the Number to import and the line’s SIP address.

2. Create a login, for outgoing calls only

   If your agent will also call out, click Create login and copy the Username and Password. The password is shown only once. Incoming calls and transfers work without a login.

3. Connect the number in Retell

   In Retell, Phone Numbers, add a number with Connect to your number via SIP trunking, and fill in:

   Field in Retell	Value
   Phone number	The Number to import, exactly as shown (for example +302101234567)
   Termination URI	The SIP address (<line ID>.sip.voicelogica.ai)
   Transport, if asked	TCP
   SIP trunk username and password	The Username and Password from step 2 (leave empty if you skipped it)

4. Assign your agent

   On the number in Retell, choose your agent for inbound calls, and for outbound calls if it will call out. Then call your number.

To send only some numbers to the agent, use an inbound route with the same SIP URI destination.

2. Transfers to your team

In Retell, add the Transfer Call function to the agent and use a cold transfer sent as SIP REFER. Voice Logica then rings the destination. Retell’s own warm transfer places a separate new call instead; on Voice Logica you get a warm transfer with the warm- prefix below.

Your line’s address is <line ID>.sip.voicelogica.ai: Retell shows it on your imported number as its termination address.

You want	Transfer to
Blind transfer to a person	sip:108@<line ID>.sip.voicelogica.ai (108 = their extension)
Blind transfer to a team	sip:<group extension>@<line ID>.sip.voicelogica.ai
Blind transfer to an outside number	+302101234567
Warm transfer to a person	sip:warm-108@<line ID>.sip.voicelogica.ai
Warm transfer to an outside number	sip:warm-+302101234567@<line ID>.sip.voicelogica.ai

Blind: the caller is passed straight on and the agent leaves the call.

Warm: the caller hears hold music while the person rings. When they answer, they are connected and the agent leaves.

Tell your team why they get the call. If your transfer settings allow custom SIP headers, add X-VL-Summary with a short summary. Voice Logica saves it with the call as the transfer reason.

Use full numbers or Voice Logica extensions. Short service numbers, emergency, premium-rate, shared-cost and satellite numbers are refused.

3. Outgoing calls from your agent

After Connect, or with the login set up by hand, your number in Retell places its calls through your Voice Logica line.

• Start them from Retell as usual: a phone call from the number, a batch call, or the Retell API.
• The person you call sees your number.
• The calls appear in Calls as outgoing, with recording and analysis.

Outgoing only. A line can be connected for outgoing calls only: your agent calls out through it and incoming calls keep going where they go today. The line then shows that your agent places its calls through this line and that incoming calls are not affected. Ask us in Support to connect it this way.

4. Transfers during outgoing calls

The same transfers work when your agent placed the call. They move the person you called:

• Blind: the person is passed on and the agent leaves.
• Warm: the person hears hold music while we ring your colleague, who sees the customer’s number. When your colleague answers, the two are connected and the agent leaves.

5. See every call analysed

• Every call, incoming and outgoing, is in Calls, including the part your team handled after a transfer.
• Each call has its recording. With analysis on, also the transcript by speaker, a summary and your call results.
• Callers are matched to your contacts, with their history, and workflows can run when a call ends.
• Your team’s own calls are analysed with the same results, so you compare the agent and your people on the same scale.

Each connected line has an Analysis switch, on by default. While it is on, each call is transcribed and, at the end, analysed by the default analysis agent in Call settings: the summary and whatever else that agent is set up to produce. That uses analysis minutes as well as trunk minutes. If you have no analysis minutes left, calls still go through, without a transcript, on trunk minutes only. Turned off, the line’s calls are never transcribed. While the connection is being rolled out, we set the switch for you.

6. Try the same agent on Voice Logica

Click Import agent on the line (or API Keys - AI platforms - Import an agent). Voice Logica copies the prompt, greeting, voice, model, transfers, tools and knowledge. Your custom functions become workflows that run during the call. Compare both in Calls, and use Update agent when you change the original. More in Try a Voice Logica agent.

If something doesn’t work

What you see	What to do
The transfer places a new call instead of passing the caller	Use a cold transfer sent as SIP REFER.
A transfer to a short number is refused	Use the full number, or the Voice Logica extension of the person or team.
Outgoing calls end at once, without ringing	Your carrier must allow this line to call out. Connect the agent to a line that can call out.
Calls are refused before they ring	Your plan has no trunk minutes left. See Billing.
Connect says the line is a Voice Logica number	Outside agents run on your own SIP trunk or office PBX. Connect that line instead.