暖转移与冷转移：如何为客服通话选择合适的转接方式

Call transfers are a decision about context: either the person picking up knows why the caller is on the line with a warm transfer, or the caller starts over with a cold transfer. The transfer type you choose shapes handle time and first-contact resolution, and it can even affect how callers rate their customer support experience.

In this article, we’ll examine the differences between a warm transfer and a cold transfer and offer guidance on choosing which type to use in customer support.

Summary

A warm transfer, also called a warm handoff or an attended transfer, gives the receiving party context before the caller connects, and a cold transfer does not.
A tepid transfer sits between the two: the destination is dialed and connected without a conference or a live introduction.
Warm transfers fit complex or sensitive issues, and cold transfers fit simple, high-volume routing.
Every warm transfer needs a short context summary and a fallback for unanswered calls.
ElevenAgents supports three transfer types, and Conference Transfer on the native Twilio integration delivers a warm transfer message to the human operator.

Warm transfer vs cold transfer: key differences

The core difference between a warm and cold transfer is how much information is passed along when the transfer is made. Warm transfers involve providing the receiving party with the caller’s context so they already understand any potential issues.

A cold transfer means the receiving party learns any context from the caller instead of the person making the transfer.

Warm transfer: The operator briefs the receiving party first, through a live introduction or a short summary, and then connects the caller.
Cold transfer: The operator connects the caller directly. The receiving party gets no advance context.
Tepid transfer: The operator dials the destination and connects the caller once someone answers, without a conference or a live introduction. Some real implementations land here, between warm and cold.

These transfer types also go by other names. A warm transfer may be referred to as a warm handoff or an attended transfer, while a cold transfer may be called a blind transfer.

Warm transfer

Tepid transfer

Cold transfer

Context for receiving party

Yes, before connection

None beyond the answered call

None

Speed

Slowest

Moderate

Fastest

Caller repeats the issue

Usually

Best for

Complex or sensitive issues

Confirmed pickup without a briefing

Simple routing to a queue

What is a warm transfer in a call center?

A warm transfer in a call center is a handoff in which the receiving party gets context about the caller before connecting the two. The first operator, human or AI, passes along who is calling and what they need. The caller picks up the conversation where it left off.

How a warm transfer works, step by step

Decide to transfer: The operator or AI agent determines the caller needs a different person or team.
Tell the caller: The operator explains who they are connecting the caller to and why.
Dial the destination: The operator calls the receiving party while the caller waits.
Provide context: The operator gives the receiving party a brief summary of the issue.
Connect the caller: The operator joins the caller to the receiving party and drops off the call.

Step four is the entire point. The context step is what makes a transfer warm. Remove it and the same sequence becomes a tepid or cold transfer.

What is a cold transfer?

A cold transfer connects the caller directly to the destination with zero advance notice to the receiving party. It is also called a blind transfer.

Cold transfers are faster because nobody waits for a briefing. The tradeoff is that the caller often has to re-explain their issue from scratch, which adds time on the second leg of the call and frustrates callers with complicated problems.

When to use warm and cold transfers

Deciding between a warm and cold transfer involves matching the type of transfer to the cost of losing context. Warm transfers take longer but are great if the type of issue means that losing context would frustrate the caller. Low-effort calls are less likely to cause issues and can use a cold transfer.

Match the transfer type to the cost of losing context. If repeating the issue would frustrate the caller or risk an error, transfer warm. If the destination needs nothing beyond the call itself, transfer cold.

Use a warm transfer for:

Complex issues: Billing disputes, technical escalations, and multi-step cases where the history matters.
Sensitive conversations: Complaints, cancellations, and health or financial matters.
High-value callers: Accounts where a repeated explanation damages the relationship.

Use a cold transfer for:

Simple routing: The caller reached the wrong department and needs the right one.
Queue destinations: The call goes to a queue rather than a specific person.
High-volume lines: Speed matters more than context, and the next agent will ask a standard set of questions anyway.

Warm transfer best practices for smoother handoffs

Warm transfers give operators all the context they need to pick up a conversation mid-flow and solve a customer’s issue as quickly as possible.

These four habits make warm transfers smoother for both callers and operators:

Keep the context summary short and specific: The receiving party needs the issue summarized. Cover who is calling, what they need, and what has already been tried in one or two sentences.
Always have a fallback: Destinations do not always answer. Decide in advance whether the operator stays on the line, takes a message, or tries a second number. Teams overlook this failure mode more than any other.
Tell the caller what happens next: Name the team they are being connected to and set expectations for the wait.
Pass along verified details: If the caller has already confirmed their identity or account number, include it so the receiving party does not ask again.

Warm transfer script template

A good warm transfer script has two pathways that run in parallel. The first of these is what the caller hears and the second is what the receiving party hears.

You can use these examples as templates for your own customer service teams:

What the caller hears

“I’m going to connect you with [team or name], who can [what they will help with]. They’ll have the details of your [issue], so you won’t need to repeat yourself. It should take about [wait time]. Is that okay?”

What the receiving party hears

“I have [caller name] on the line. They’re calling about [issue]. [Identity or account details already verified.] They’ve already tried [what has been tried]. They need [desired outcome].”

Example

Caller hears: “I’m connecting you with our technical support team now. They’ll have the details of your login problem, so you won’t need to repeat yourself.”
Receiving party hears: “I have Jordan Lee on the line. Identity is verified. Their account was locked after three failed password resets, and they need access restored today.”

In ElevenAgents, the first message maps to client_message and the second to agent_message, which are covered in the next section.

How AI voice agents route and transfer calls

AI voice agents transfer calls through tools they trigger when a defined condition is met, such as when a caller asks for a human. In ElevenAgents, the transfer_to_number system tool hands a live phone call to an external phone number or SIP URI.

The tool supports three transfer types, each with different warm transfer support:

Conference Transfer: The default. The agent dials the destination, adds the participant to a conference, and then leaves so only the caller and the human remain. On the native Twilio integration, it reads a warm transfer message to the human operator.
Blind Transfer: The call goes directly to the destination with no warm message. It preserves the original caller ID and requires a number imported through the native Twilio integration.
SIP REFER Transfer: The call moves using the SIP REFER protocol and reaches phone numbers or SIP URIs. It is available on SIP calls only and does not support a warm message.

The warm transfer mechanism comes down to two parameters:

client_message: What the caller hears while waiting for the transfer.
agent_message: The context summary delivered to the human operator receiving the call.

The agent_message is literally what makes the transfer warm. For example, the caller hears "I'm connecting you with a billing specialist now," and the specialist hears "Caller was charged twice on their March invoice and wants the duplicate refunded."

ElevenAgents also includes transfer_to_agent for AI-to-AI handoffs, such as a general agent routing to a billing specialist agent. That tool moves the conversation between AI agents. transfer_to_number moves it to a human.

How to set up a warm transfer with ElevenAgents

A warm transfer in ElevenAgents requires the Transfer to Number tool, a transfer rule, and a phone number imported through the native Twilio integration. Setup takes four steps.

Enable the tool: In your agent's configuration, add a tool and choose "Transfer to Human." This enables the transfer_to_number system tool.
Configure the destination: Create a transfer rule with Conference as the transfer type and enter the phone number in E.164 format. SIP URI destinations require SIP REFER, which does not carry a warm message.
Define the trigger condition: Describe in natural language when the transfer happens, such as "User explicitly requests to speak to a human."
Shape both messages: The agent generates client_message and agent_message at transfer time. Use the tool description and your agent's system prompt to specify what each one contains.

Before launch, test the no-answer and busy-line paths. Call the agent, trigger the transfer to a line that will not pick up, and confirm the caller's experience matches your fallback plan. The agent testing tools cover the conversation logic that leads to the transfer.

What happens when no one answers a transfer in ElevenAgents?

The exact workflow that occurs when the destination doesn't answer depends on the transfer type and your telephony setup. Plan the fallback for each type you use.

Conference Transfer: The agent stays in the conference until the destination picks up. If the line rings out, returns a busy signal, or reaches an external voicemail, the agent remains on the call. What happens next depends on how your telephony carrier or SIP trunk is configured: the call can ring indefinitely, the carrier can disconnect it, or the agent can hear the voicemail or busy signal.
Blind Transfer: ElevenAgents redirects the call to the new destination and disconnects the agent immediately. If the destination doesn’t answer, the receiving carrier or phone system decides what happens, such as going to personal voicemail or ringing out. The agent cannot step back in. On the native Twilio integration, a Blind Transfer currently has to be set up through the JSON editor in the UI.
SIP REFER Transfer: Once your SIP server accepts the REFER request, the agent ends its session. Any no-answer routing, such as sending the caller back to a queue, an IVR, or a backup person, has to be configured on your own SIP trunk or PBX.

In every case, what the caller will experience depends on how your carrier, SIP trunk, or phone system is configured. Be sure to check this before launch.

There are two settings you can configure to help with the no-answer path:

Carrier-level forwarding: If you transfer to a mobile or landline number, set up conditional call forwarding for busy or no-answer so callers reach a backup queue or voicemail.
SIP-level failover: If you use SIP trunking, configure your PBX to route the call to a secondary destination or an automated queue when the primary extension returns a 486 Busy or 480 Temporarily Unavailable response, or times out.

Together, these settings keep callers from being left on a line that rings out. Read our SIP trunking documentation for the technical details.

Get started with ElevenAgents for smarter call transfers

ElevenAgents gives your team control over every handoff: which calls transfer, where they go, and what the human operator knows before saying hello. Callers explain their issue once, and your operators start every transferred call with context.

Read the Transfer to Number documentation for the full configuration reference, or create an account to build your first agent today.