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This guide shows the pattern for placing outbound calls with your AI voice agent over Vobiz. Vobiz provides the SIP trunk and caller-ID number that carry the call to the public phone network; your agent platform (Vapi, Retell, ElevenLabs, LiveKit, Bolna, Ultravox, or a self-hosted pipeline) drives the conversation once the call connects.
The exact steps differ per platform. This guide explains the shared outbound pattern and the credentials you map between systems. For click-by-click steps and screenshots, follow your platform’s integration page under Integrations.

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How outbound works

Your app / platform → AI agent platform → Vobiz outbound SIP trunk → phone network → recipient
Your platform authenticates to your Vobiz outbound trunk with a SIP domain, username, and password, then dials the recipient using your Vobiz number as caller ID.

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Prerequisites

  • A Vobiz account with active balance (outbound calls consume credit).
  • A Vobiz phone number to use as caller ID.
  • An account on your chosen AI voice platform, with an agent already created.

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Step 1: Create an outbound trunk in Vobiz

1

Create the trunk

In the Vobiz Console, go to SIP Trunk → Outbound Trunks → Trunks and click + Create Trunk. Name it (for example, AI Agent Outbound).
2

Attach a credential

Under Authentication & Linking, select an existing credential or create a new one, then save the trunk.
3

Copy the connection details

From the Authentication & Linking section, copy:
FieldExample
SIP domain<your_unique_domain>.sip.vobiz.ai
Username<your_username>
Password<your_password>
Use the exact SIP domain - never a generic sip.vobiz.ai.

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Step 2: Connect the trunk on your AI platform

Paste the three Vobiz values into your platform’s outbound SIP trunk. The field names vary, but the mapping is always the same:
Vobiz valueCommon platform field name
SIP domainGateway URL / Address / Termination URI
UsernameSIP username / auth_username
PasswordSIP password / auth_password
Your Vobiz numberCaller ID / from / numbers
When a platform asks for a Termination URI or Address, enter the SIP domain without the sip: prefix - hostname only.
Examples of how this looks per platform (see each integration page for full steps):
  • Vapi / Retell / ElevenLabs: add a SIP trunk credential with the domain + username + password, then import your Vobiz number as a BYO SIP number.
  • LiveKit: create_sip_outbound_trunk(address=sip_domain, auth_username=username, auth_password=password, numbers=[your_number]).
  • Ultravox / Bolna: pass the Vobiz credentials in the call-start request or provider settings.

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Step 3: Place a call

Trigger an outbound call from your platform (a single call, a batch, or via the platform API). Select your imported Vobiz number as the caller ID and your AI agent as the assistant. When the recipient answers, your agent speaks.
Your AI agent can now place outbound calls through Vobiz SIP infrastructure.

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Self-hosted pipelines (Pipecat / Dograh / custom)

If you run your own pipeline, you can dial out with the Vobiz Call API and let Vobiz fetch a <Stream> instruction that points at your WebSocket: 
curl -X POST https://api.vobiz.ai/api/v1/Account/YOUR_AUTH_ID/Call/ \
  -H "X-Auth-ID: YOUR_AUTH_ID" \
  -H "X-Auth-Token: YOUR_AUTH_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "+918011223344",
    "to": "+919148223344",
    "answer_url": "https://your-server/answer",
    "answer_method": "POST"
  }'
Your /answer route returns a <Stream> response and audio flows over the WebSocket. See WebSockets and Pipecat.

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Optional: call transfer to a human

Most platforms support transferring the AI call to a live agent (blind/cold transfer over SIP REFER). The agent constructs a SIP URI like sip:+15550001234@<your-sip-domain> and initiates the transfer. Enable Call Transfer (SIP REFER) on your Vobiz trunk and configure the destination on the platform. See the transfer sections of the LiveKit and Vapi guides.

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Troubleshooting

  • 401 Unauthorized: the username/password on the platform trunk don’t match your Vobiz outbound trunk.
  • Call fails silently / doesn’t connect: you used a generic sip.vobiz.ai instead of your exact <id>.sip.vobiz.ai, or left a sip: prefix on the domain.
  • Insufficient balance: outbound calling needs Vobiz credit - top up in the Console.
  • Phone number format error: use E.164 (+919148223344); confirm the number is active in Vobiz.

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Next steps