### Answer Yes, this is possible with Retell AI. You would typically set this up as a call overflow or after-hours routing scenario using your telephony provider's call forwarding rules combined with Retell AI. Here's how it works: 1. Configure your telephony system (e.g., Twilio, Telnyx, or your PBX) to forward calls to your Retell AI agent after a set number of rings or if no one answers. [(1) ]() 2. Use Elastic SIP Trunking or Dial to SIP URI to route those forwarded calls to Retell. With Elastic SIP Trunking, you configure your number's origination settings to point to Retell's SIP server:

sip:sip.retellai.com

3. For inbound calls, Retell supports different transport methods (TCP, UDP, TLS) and you can set up the SIP server URL accordingly. The call routing logic (e.g., "ring for 20 seconds, then forward to Retell AI") is handled on your telephony provider's side, not within Retell itself. Once the call is forwarded to Retell, your AI agent picks up and handles the conversation. This approach is commonly used for after-hours call answering and call overflow scenarios where AI phone agents can support callers when human agents are unavailable. [(2) ]() Check out these resources for setup details: - [Custom Telephony Overview]() - [2025 B2B Guide to AI Phone Calls]()

​ To learn more, see the sources I considered: [[1] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) [[2] 2025 B2B Guide to AI Phone Calls & Voice Agents | Retell AI | Retell AI](https://www.retellai.com/blog/b2b-guide-to-ai-phone-calls) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer Yes, this is possible using Retell AI's warm transfer feature. With warm transfer, a human agent can join the call while the AI is still conversing with the caller. [(1) ]() Here's how it works: - Warm transfer creates a three-way call where the AI agent, the caller, and the human agent are all connected. [(2) ]() - The AI can deliver a whisper message privately to the human agent before connecting them to the caller, providing context about the conversation. [(1) ]() - Optionally, a three-way message can be spoken to both the caller and the human agent once the connection is established. - Once the human agent is connected and ready, the AI agent hangs up, leaving the caller with the human. [(2) ]() You can also configure: - Human detection to confirm a real person has answered before completing the transfer [(1) ]() - On-hold music for the caller while waiting for the human agent This is different from a cold transfer, where the call is simply handed off without any context or AI involvement during the transition. For setup details, see: - [Transfer call]() - [Call Transfer Node]()

​ To learn more, see the sources I considered: [[1] Transfer call](https://docs.retellai.com/build/single-multi-prompt/transfer-call) [[2] Warm Transfer vs Cold Transfer - The AI Advantage in Call Centers | Retell AI](https://www.retellai.com/blog/effortless-handoffs-with-retell-ais-warm-transfer-feature) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer Yes, Retell AI can initiate a call to another number while conversing with a person using the Transfer Call feature. [(1) ]() When the AI agent triggers a transfer (either warm or cold) , it dials out to the transfer destination while the original caller is still on the line. - **Cold transfer**: The call is transferred to a destination number and the AI disconnects. - **Warm transfer**: The AI dials the transfer destination, and once connected, can facilitate a three-way conversation. The AI can deliver a whisper message privately to the receiving party, then optionally speak a three-way message to both parties before completing the handoff. , [(2) ]() During a warm transfer, the original caller hears on-hold music while the AI is dialing and connecting to the transfer target. [(1) ]() So in essence, the AI is making an outbound call to another party while still managing the conversation with the original caller. If you're asking about making a completely separate, independent outbound call while simultaneously handling an inbound call—that would require a separate call instance rather than a transfer within the same call session. The sources don't explicitly document that capability.

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

​ To learn more, see the sources I considered: [[1] Transfer call](https://docs.retellai.com/build/single-multi-prompt/transfer-call) [[2] Warm Transfer vs Cold Transfer - The AI Advantage in Call Centers | Retell AI](https://www.retellai.com/blog/effortless-handoffs-with-retell-ais-warm-transfer-feature) ​

### Answer Yes, this is possible using Retell AI's warm transfer feature. [(1) ]() Here's how it would work in your scenario: 1. You miss a call → Your telephony system forwards it to Retell AI 2. Retell AI picks up and converses with the caller 3. You become available and want to join → The AI can initiate a warm transfer to your number With warm transfer: [(2) ]() - The AI dials out to you while keeping the caller on hold with on-hold music [(1) ]() - The AI can deliver a whisper message privately to you, briefing you on the conversation context before connecting you to the caller - Optionally, a three-way message can be spoken to both you and the caller once connected - Human detection can confirm you've answered before completing the transfer The key point: **you would need to trigger the transfer**—either by the AI being prompted to transfer (e.g., caller requests a human) , or by configuring a custom function that allows you to signal the AI to initiate the transfer to you. However, the sources don't document a way for you to spontaneously "barge in" to an active Retell AI call without the AI initiating the transfer. The transfer must be initiated from the AI agent's side using the Transfer Call tool. For setup details, see: - [Transfer call]() - [Transfer Call Node]()

​ To learn more, see the sources I considered: [[1] Transfer call](https://docs.retellai.com/build/single-multi-prompt/transfer-call) [[2] Warm Transfer vs Cold Transfer - The AI Advantage in Call Centers | Retell AI](https://www.retellai.com/blog/effortless-handoffs-with-retell-ais-warm-transfer-feature) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer The whisper message is a private, pre-connection message spoken only to the transfer target (the human agent) before they are connected to the original caller. [(1) ]() Here's how it works in a warm transfer: 1. The AI agent initiates the warm transfer and dials the transfer destination 2. The original caller is placed on hold with on-hold music 3. Once the transfer target picks up, the AI delivers the whisper message privately to them—the caller does not hear this [(2) ]() 4. This whisper message briefs the receiving agent on the reason for the transfer and relevant context, so the customer doesn't have to repeat themselves 5. After the whisper message, the caller is then connected to the human agent The whisper message can include details like: [(3) ]() - Why the call is being transferred - Customer authentication status - Relevant conversation context - Recommended next steps This ensures the human agent is fully informed and prepared before speaking with the caller, creating a seamless handoff experience. [(2) ]() You configure the whisper message content in the warm transfer settings when setting up the Transfer Call function. [(1) ]()

​ To learn more, see the sources I considered: [[1] Transfer call](https://docs.retellai.com/build/single-multi-prompt/transfer-call) [[2] Warm Transfer vs Cold Transfer - The AI Advantage in Call Centers | Retell AI](https://www.retellai.com/blog/effortless-handoffs-with-retell-ais-warm-transfer-feature) [[3] ](https://www.retellai.com/resources/retell-ai-fraud-alert-engine-voice-biometrics-warm-transfers-chargeback-reduction) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer To add a whisper message, you configure it within the warm transfer settings when setting up the Transfer Call function. [(1) ]() Here's how: 1. Add the Transfer Call Tool – Click "+ Add" in the tools section and select "Transfer Call" from the dropdown menu 2. Select Warm Transfer – Choose "warm transfer" as your transfer type 3. Configure Warm Transfer Specific Settings – In the warm transfer settings section, you'll find the *Whisper message (optional) * field 4. Enter your whisper message – This is the message spoken privately to the transfer target before connecting them to the original caller If you're using Conversation Flow, the process is similar—configure the whisper message within the warm transfer specific settings on the Call Transfer Node. [(2) ]() The whisper message is delivered after the transfer target picks up but before the caller is connected, giving the receiving agent context about the call. [(3) ]() For detailed setup, see: [Transfer call]() and [Call Transfer Node]()

​ To learn more, see the sources I considered: [[1] Transfer call](https://docs.retellai.com/build/single-multi-prompt/transfer-call) [[2] Call Transfer Node](https://docs.retellai.com/build/conversation-flow/call-transfer-node) [[3] Warm Transfer vs Cold Transfer - The AI Advantage in Call Centers | Retell AI](https://www.retellai.com/blog/effortless-handoffs-with-retell-ais-warm-transfer-feature) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

​ To learn more, see the sources I considered: [[1] Transfer call](https://docs.retellai.com/build/single-multi-prompt/transfer-call) [[2] Warm Transfer vs Cold Transfer - The AI Advantage in Call Centers | Retell AI](https://www.retellai.com/blog/effortless-handoffs-with-retell-ais-warm-transfer-feature) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer Not quite simultaneously in the way you might be thinking. Here's what actually happens during a **warm transfer**: 1. The AI initiates the transfer by dialing out to the human agent [(1) ]() 2. The original caller is placed on hold with on-hold music while the transfer destination is being dialed 3. Once the human agent picks up, the AI can deliver a whisper message privately to brief them 4. Then the caller is connected to the human agent [(2) ]() So the AI isn't actively conversing with the customer while simultaneously calling the human agent—the customer hears on-hold music during that dialing phase. [(1) ]() The warm transfer creates a three-way call scenario where the AI, caller, and human agent are eventually all connected, but the caller is on hold during the initial dial-out to the human. [(2) ]() You configure when the transfer happens through your prompt (e.g., "If the user requests a human, use the transfer_call tool") . [(1) ]()

### Answer Correct—the AI cannot actively converse with the customer and dial the human agent at the exact same time. [(1) ]() During a warm transfer, the caller is placed on hold with on-hold music while the AI dials out to the transfer destination. Once the human agent picks up, the AI delivers the whisper message privately, and then the caller gets connected. [(2) ]() So the sequence is: 1. AI triggers the transfer 2. Caller goes on hold (hears on-hold music) 3. AI dials the human agent 4. Human answers → AI delivers whisper message 5. Caller is connected to the human The "three-way" aspect happens after the dial-out completes, not during simultaneous conversation with both parties.

​ To learn more, see the sources I considered: [[1] Transfer call](https://docs.retellai.com/build/single-multi-prompt/transfer-call) [[2] Warm Transfer vs Cold Transfer - The AI Advantage in Call Centers | Retell AI](https://www.retellai.com/blog/effortless-handoffs-with-retell-ais-warm-transfer-feature) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.