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] Send & receive SMS](https://docs.retellai.com/deploy/enable-sms) [[2] TEXT MESSAGE ISSUE](https://discord.com/channels/1186424376300679209/1424595052595904542) [[3] SMS is not sent.](https://discord.com/channels/1186424376300679209/1460659178120024096) ​

### Answer This error means your phone number hasn't completed the A2P (Application-to-Person) registration process required for SMS capabilities. [(1) ]() To resolve this, you need to enable SMS capabilities for your phone number: For Retell Twilio Numbers: 1. Get approved for a business profile (free) 2. Get approved for the brand based on business profile ($4 one-time fee for low-volume or $45 for standard) 3. Get approved for an SMS campaign ($15 one-time fee) The entire application process can take around 2-3 weeks, sometimes longer, as it's a manual review process on the telephony provider side. For Custom Twilio Numbers: If you're bringing your own Twilio number, you need to: 1. Click on "Setup SMS Function" in Advanced Add-Ons in your phone number settings 2. Provide your Twilio Account SID and Auth Token 3. Make sure your Twilio number already has SMS capabilities enabled and is compliant with SMS regulations before integration Important limitations: [(1) ]() [(2) ]() - SMS capabilities are currently limited to US numbers only - Telnyx is not supported yet for SMS [(3) ]()

### Answer You're correct. In Conversation Flow, the SMS Node transitions based on whether the SMS was successfully sent or failed—not on receiving a response from the recipient. [(1) ]() Specifically, the node transitions to the next node once the SMS is successfully sent or fails to send, which should take less than 2 seconds. The transition happens purely based on the SMS delivery result, not on any reply or response from the user. This means your conversation flow will continue immediately after the SMS is sent, regardless of whether the recipient reads or responds to the message.

​ To learn more, see the sources I considered: [[1] SMS Node](https://docs.retellai.com/build/conversation-flow/sms-node) ​

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

### Answer To wait for a user's response in Conversation Flow, use a Conversation Node after your SMS Node. [(1) ]() Conversation Nodes are designed to handle dialogue and user interactions. When you place a Conversation Node after the SMS Node, the agent will naturally wait for and respond to what the user says next during the phone call. The SMS Node itself doesn't wait for SMS replies—it transitions immediately after the SMS is sent or fails (within 2 seconds) . [(2) ]() However, agents can receive SMS during an active call and understand the content, including text, images, audio, and video. This works out of the box for Retell Twilio numbers and custom telephony numbers that passed A2P applications. So your flow would be: 1. SMS Node sends the message 2. Conversation Node waits for the user's verbal response during the call 3. If the user sends an SMS reply during the call, the agent can understand it

​ To learn more, see the sources I considered: [[1] Node Overview](https://docs.retellai.com/build/conversation-flow/node) [[2] SMS Node](https://docs.retellai.com/build/conversation-flow/sms-node) ​

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