> ## Documentation Index
> Fetch the complete documentation index at: https://docs.voiceinfra.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Smart AI Call Transfers: Cold, Warm & Attended Warm

> Configure AI-to-human call handoffs in VoiceInfra. Choose cold, warm, or attended warm transfer with context briefing, keypad routing, and CSV import.

Your AI agent handles the majority of calls on its own — but some conversations are too complex, too sensitive, or too valuable to stay fully automated. VoiceInfra's call transfer feature lets your agent recognise those moments and hand off the call to a human agent, team queue, or external number, smoothly and without losing context. You choose exactly how the handoff works: a fast cold drop-off, a reassuring warm bridge, or a fully attended transfer where the AI briefs the human before stepping back.

## Transfer types

| Type                           | How it works                                                                  | Best for                               |
| ------------------------------ | ----------------------------------------------------------------------------- | -------------------------------------- |
| **Cold Transfer** (SIP Refer)  | AI connects the caller to the destination, then drops off immediately         | Simple escalations, fast handoff       |
| **Warm Transfer** (SIP Invite) | AI stays on the line during the handoff until the human agent answers         | Complex issues, continuity matters     |
| **Attended Warm Transfer**     | AI bridges both parties, briefs the human agent with context, then steps back | VIP callers, context-critical handoffs |

## Attended warm transfer

Attended Warm Transfer is the most thorough handoff mode VoiceInfra offers. When a transfer is triggered, your AI agent stays connected to **both** the caller and the human agent simultaneously — neither party is left in silence. The AI uses your configured **context instructions** to verbally brief the human agent on what the caller needs, what has already been discussed, and any important details, before quietly stepping back once the handoff is complete.

If the transfer target is unavailable or doesn't answer, the AI plays the **decline message** you configure, so callers always receive a professional response rather than an awkward silence or an unexpected busy signal.

<Note>
  Attended Warm Transfer is the recommended mode for VIP callers, high-value accounts, or any situation where a human agent needs context before picking up the conversation.
</Note>

## Setting up call transfers

<Steps>
  <Step title="Open the Call Transfer tab">
    In your agent configuration, navigate to the **Call Transfer** tab.
  </Step>

  <Step title="Select a transfer type">
    Choose **Cold Transfer** (SIP Refer), **Warm Transfer** (SIP Invite), or **Attended Warm Transfer** based on your use case. You can configure multiple transfer destinations each using the same type.
  </Step>

  <Step title="Add destinations">
    Add one or more transfer destinations. Each destination accepts a phone number, SIP URI, or internal extension. Give each destination a descriptive label (for example, "Billing Team" or "Tier-2 Support") so your agent can reference it correctly.
  </Step>

  <Step title="Set a transfer message">
    Write the message your AI agent will say to the caller immediately before initiating the transfer — for example, *"Let me connect you with one of our specialists now."* This keeps the caller informed and reduces perceived wait time.
  </Step>

  <Step title="Add context instructions (Attended Warm only)">
    If you selected Attended Warm Transfer, add **context instructions** — the script your AI agent will use to brief the human agent. Include the caller's name, the issue category, any key details already gathered, and anything the human needs to know before taking over.
  </Step>

  <Step title="Configure a decline message">
    Set the **decline message** your agent will play if the transfer target is unavailable. Offer alternatives where possible — for example, *"I'm sorry, our billing team is unavailable right now. I can schedule a callback or take a message."*
  </Step>

  <Step title="Configure Caller ID (Warm transfers only)">
    For Warm Transfers, choose whether to pass through the caller's original number or use a custom Caller ID on the outbound leg. This controls what the receiving agent sees when they pick up.
  </Step>
</Steps>

## Transfer destinations

VoiceInfra supports three destination formats, and you can mix them freely within the same agent:

<CardGroup cols={3}>
  <Card title="Phone numbers (PSTN)" icon="phone">
    Standard E.164 format numbers such as `+14155550100`. Routes over the public telephone network to any mobile or landline.
  </Card>

  <Card title="SIP URIs" icon="server">
    Full SIP addresses such as `sip:agent@company.com`. Routes directly over SIP to a softphone, PBX extension, or SIP trunk endpoint.
  </Card>

  <Card title="PBX extensions" icon="building">
    Internal extension numbers such as `500`. Routes within your PBX without consuming external trunk capacity.
  </Card>
</CardGroup>

For PBX systems that require post-connection DTMF (for example, pressing an extension number after the call is answered by a hunt group), enable **Dial extension after answer**. The agent automatically sends the DTMF digits once the destination picks up.

## Keypad routing (AI-driven IVR)

Keypad routing lets callers press digit codes mid-conversation to self-route to specific destinations — without you needing to rebuild a traditional IVR tree. Your AI agent listens for the keypress, maps it to a destination, and transfers the call instantly.

Configure a mapping of 1–5 digit codes to destinations in the **Keypad Routing** section of your agent:

| Key | Destination       |
| --- | ----------------- |
| `1` | Billing team      |
| `2` | Technical support |
| `3` | VIP queue         |

You can reference these options naturally in your agent's system prompt — for example: *"If you'd like to speak with billing, press 1 at any time."*

## Bulk setup via CSV

If you have many transfer destinations or complex routing rules, use the CSV import feature to configure everything at once:

1. Click **Download Template** to get a pre-formatted CSV with the correct column structure.
2. Fill in destination names, phone numbers or SIP URIs, transfer messages, and keypad codes.
3. Upload the completed file to populate all your routing rules in a single step.

You can also export your current configuration as CSV at any time for backup or bulk edits.

## Pricing

| Action                 | Cost                 |
| ---------------------- | -------------------- |
| Standard call transfer | \$0.025 per transfer |

<Note>
  Transfer costs are charged per transfer event, not per minute. Standard per-minute call rates still apply for the duration of the transferred call.
</Note>

## Frequently asked questions

<AccordionGroup>
  <Accordion title="When should I use Attended Warm Transfer?">
    Use Attended Warm Transfer for VIP callers, high-value accounts, or complex issues where the human agent needs context before picking up. The AI's verbal briefing prevents the caller from having to repeat themselves, which significantly improves satisfaction for sensitive or high-stakes conversations.
  </Accordion>

  <Accordion title="What happens if the transfer target is unavailable?">
    If the target doesn't answer or is unavailable, your AI agent plays the **decline message** you configured. You can customise this message to offer alternatives — a callback, a voicemail, or routing to another destination — so callers are never left without a response.
  </Accordion>

  <Accordion title="Can I control what Caller ID the transfer shows?">
    Yes, but only for Warm Transfers. You can choose to pass through the caller's original number or substitute a custom number. Cold Transfers use the default system Caller ID.
  </Accordion>

  <Accordion title="Is keypad routing the same as IVR?">
    They serve a similar purpose but work differently. Traditional IVR presents a rigid menu at the start of a call. Keypad routing in VoiceInfra is AI-driven and mid-conversation — callers can press a code at any point while speaking naturally, and the agent responds contextually before routing them. There's no menu tree to maintain.
  </Accordion>

  <Accordion title="What destination formats does VoiceInfra support?">
    You can add standard phone numbers in E.164 format (`+14155550100`), full SIP URIs (`sip:user@domain.com`), or plain internal extension numbers. All three formats work seamlessly in the same agent configuration.
  </Accordion>

  <Accordion title="Does call transfer work with my existing PBX?">
    Yes. VoiceInfra uses standard SIP Refer (cold) and SIP Invite (warm/attended) protocols, making it compatible with virtually any PBX system, SIP trunk, or cloud telephony provider — including Cisco, Avaya, 3CX, Asterisk, and Yeastar.
  </Accordion>
</AccordionGroup>