### Answer To connect your Twilio number to Retell, use the "Connect via SIP Trunking" option—there isn't a separate "Add Twilio number" button. [(1) ]() , [(2) ]() ## Steps to Connect Your Twilio Number 1. Set up Elastic SIP Trunking in Twilio: [(1) ]() - Create a new SIP trunk in Twilio (search "SIP trunk" → select "Elastic SIP Trunks") , [(3) ]() - Enable call transfer and PSTN transfer - Set up Termination (for outbound) : create a termination SIP URI and set up authentication with username/password [(1) ]() - Set up Origination (for inbound) : use Retell's SIP server address

sip:sip.retellai.com

- Move your Twilio number to this SIP trunk under the "Numbers" tab , [(3) ]() 2. Import the number to Retell: [(1) ]() - Go to Phone Numbers → click the plus icon → select "Connect via SIP Trunking" [(3) ]() - Enter your phone number, the Termination SIP URI from Twilio, and your SIP credentials (username/password) [(1) ]() , [(3) ]() 3. For SMS specifically: [(4) ]() If you already have SMS capabilities enabled on your Twilio number, go to your phone number settings in Retell and click "Setup SMS Function" under Advanced Add-Ons, then provide your Twilio Account SID and Auth Token. There's also a helpful video walkthrough: [Retell AI - Connect to your own Twilio - Using Sip Trunking]() [(3) ](

be.com/watch?v=JC3PV_R-Z1Y)

​ To learn more, see the sources I considered: [[1] Twilio](https://docs.retellai.com/deploy/twilio) [[2] Enable the Twilio provider module](https://community.retellai.com/t/enable-the-twilio-provider-module/178) [[3] Retell AI - Connect to your own Twilio - Using Sip Trunking]() [[4] Send & receive SMS](https://docs.retellai.com/deploy/enable-sms) ​

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

will it work immediately ? the phone number is already A2P approved. This is a long process for this Sadly :/ @AI Evy

### Answer Once your SIP trunk is properly configured in Twilio and the number is imported to Retell, calls should work without additional delays on Retell's side. [(1) ]() However, there are a few things to keep in mind: Retell won't validate your configuration until a call is made — the system won't throw errors if details or configuration are incorrect until you actually attempt a call. Troubleshooting tips if calls don't connect: - For inbound issues: check your origination settings in your SIP trunking provider and review logs on the Twilio side - For outbound issues: verify your termination settings and ensure you provided the correct termination URI to Retell Since your number is already A2P approved, that approval carries over — you don't need to re-register with Retell. The SIP trunk setup is just routing configuration. I understand the process feels lengthy, but once the SIP trunk is configured correctly, your imported number should function like any Retell-purchased number for making and receiving calls. [(2) ]()

​ To learn more, see the sources I considered: [[1] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) [[2] AI in SIP Calling & Telephony Solutions | Retell AI](https://www.retellai.com/blog/integrating-ai-with-sip-trunking-and-modern-telephony) ​

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

This is JUST for SMS. NO calls needed at this time @AI Evy

### Answer For SMS-only with your own Twilio number (no voice calls needed) , you still need to connect via SIP trunking first, then configure SMS separately. [(1) ]() Steps for SMS with your own Twilio number: 1. Import the number via SIP trunking — even for SMS-only, the number needs to be imported to Retell through the SIP trunk connection process [(2) ]() 2. Set up SMS Function in Retell: - Navigate to your phone number settings in the Retell dashboard - Click on "Setup SMS Function" under Advanced Add-Ons - Enter your Twilio Account SID and Twilio Auth Token (found in your Twilio Console under Account Info) [(1) ]() 3. Once credentials are verified, your Twilio number will be integrated with Retell's SMS capabilities for: - Sending one-way SMS during calls - Setting up two-way SMS conversations (requires enabling

useInboundWebhookOnNumberCalled

) Important notes: - Your Twilio number must already have SMS capabilities enabled and be A2P compliant before integration - Since yours is already A2P approved, that approval carries over - Current SMS capabilities are limited to US numbers only The SIP trunk setup is required for Retell to recognize and route to your number, even if you're only using SMS functionality. [(3) ]() , [(4) ]()

​ To learn more, see the sources I considered: [[1] Send & receive SMS](https://docs.retellai.com/deploy/enable-sms) [[2] Twilio](https://docs.retellai.com/deploy/twilio) [[3] Discord message from @cartier5 on 2025-04-24](https://discord.com/channels/1186424376300679209/1186462578310910112/1365089588649136138) [[4] Discord message from @mushrooooom on 2025-06-26](https://discord.com/channels/1186424376300679209/1186462578310910112/1387632326682611873) ​

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

### Answer The

useInboundWebhookOnNumberCalled

setting is required when you bring your own Twilio number and want two-way SMS (meaning users can reply to your messages and the AI responds back) . [(1) ]() , [(2) ]() Here's how it works: - One-way SMS (agent sends texts to users, no replies expected) : Works after you set up the SMS Function with your Twilio credentials—no extra configuration needed. [(1) ]() - Two-way SMS (users can reply and the AI agent responds) : Requires enabling

useInboundWebhookOnNumberCalled

. Where to configure it: This setting is **not available in the Retell dashboard UI**—it can only be enabled through the API. [(2) ]() What you also need for two-way SMS: - Attach a chat agent (not just a voice agent) to your phone number for inbound and outbound SMS [(1) ]() - The chat agent handles the SMS conversations [(2) ]() In simple terms: 1. Set up SMS Function with your Twilio credentials (dashboard) [(1) ]() 2. Attach inbound and outbound SMS agents to your number (dashboard) [(2) ]() 3. Enable

useInboundWebhookOnNumberCalled

via API if you want two-way conversations If you only need to send SMS (one-way) , you can skip the webhook configuration. [(1) ]()

​ To learn more, see the sources I considered: [[1] Send & receive SMS](https://docs.retellai.com/deploy/enable-sms) [[2] Chat Agents not sending out texts to Twillio](https://discord.com/channels/1186424376300679209/1463233659208339668) ​

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

### Answer --- The authentication setup is required for your Elastic SIP Trunk to accept outbound requests from Retell. [(1) ]() How to set up authentication in Twilio: In your Twilio Elastic SIP Trunk's Termination settings, you need to either whitelist IP addresses or create credentials with a username and password. For the credentials route (recommended since Retell doesn't have a static IP) : [(2) ]() 1. In the Termination section, Twilio will prompt you to set up credentials 2. Give your credentials a friendly name 3. Create a username and password — Twilio requires the password to be at least 12 characters long, with one uppercase letter, one lowercase letter, a special symbol, and a digit 4. Save your credentials When importing the number to Retell: Supply the termination SIP URI you set up, along with the username and password you created. [(1) ]() Note: The username is different from the "friendly name" shown in the credential list — make sure you use the actual username you created. You can also import programmatically via the API by including

sip_trunk_auth_username

and

sip_trunk_auth_password

parameters. [(3) ]()

​ To learn more, see the sources I considered: [[1] Twilio](https://docs.retellai.com/deploy/twilio) [[2] Retell AI - Connect to your own Twilio - Using Sip Trunking]() [[3] Import Phone Number](https://docs.retellai.com/api-references/import-phone-number) ​

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

what do i put for orgiination SIP URI @AI Evy

### Answer For the Origination SIP URI in Twilio (used for inbound calls) , enter Retell's SIP server address: [(1) ]()

sip:sip.retellai.com

, [(2) ]() In the video walkthrough, after setting up Termination, you tap on Origination in the left menu, then click to create an Origination URI and paste this address. [(3) ]()

​ To learn more, see the sources I considered: [[1] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) [[2] Vonage](https://docs.retellai.com/deploy/vonage) [[3] Retell AI - Connect to your own Twilio - Using Sip Trunking]() ​

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

### Answer No, you do not need to redo the A2P registration process with Retell if you're bringing your own Twilio number that's already A2P approved. [(1) ]() What you've done (Setup SMS Function with SID/Auth Token) should be sufficient for using your existing Twilio SMS capabilities through Retell. The A2P registration process shown in the Retell dashboard (business profile → brand → campaign) is specifically for Retell Twilio numbers, not for numbers you bring yourself. , [(2) ]() For your own Twilio number: - Your existing A2P approval on Twilio carries over [(1) ]() - You just need to provide your Twilio Account SID and Auth Token in the "Setup SMS Function" under Advanced Add-Ons - Once verified, your number is integrated with Retell's SMS capabilities Important caveat: For custom telephony/BYOC numbers, Retell's built-in SMS dashboard features may not work directly—you may need to handle SMS through your own automation. [(3) ]() , [(4) ]() One community member noted: "our send sms won't work through our dashboard, you'll have to use your own chat automation for it" for BYOC numbers. [(3) ]() If you run into issues where SMS isn't sending even after setup, double-check that your Twilio credentials saved correctly—some users have reported the modal closing without confirmation. [(5) ]()

​ To learn more, see the sources I considered: [[1] Send & receive SMS](https://docs.retellai.com/deploy/enable-sms) [[2] A2P Setup ultra guide | Enable SMS for Your Retell Agent]() [[3] Discord message from @co.abdullah on 2025-12-12](https://discord.com/channels/1186424376300679209/1186462578310910112/1448882948655943680) [[4] Phone number can send SMS](https://discord.com/channels/1186424376300679209/1387874084536193024) [[5] Setup SMS Function Not Saving for Twilio Integration](https://discord.com/channels/1186424376300679209/1446220160213061865) ​

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

So am I good to receive both inbound and send outbound texts now from this number? @AI Evy

### Answer Based on the sources, there's an important limitation you should be aware of: For custom telephony/BYOC Twilio numbers, SMS functionality through Retell's dashboard may not work. [(1) ]() One community member confirmed: "for any sms, if you're using custom telephony it must be done through your side" and "sms only works with retell twilio numbers as of right now." What this means for you: - Outbound SMS from Retell dashboard: Likely won't work with your BYOC number—you'd need to send SMS through your own Twilio setup/automation - Two-way SMS via Retell: Only Retell-issued Twilio numbers fully support two-way SMS through the platform currently [(2) ]() Your options: 1. Handle SMS through your own Twilio automation (since your number is already A2P approved there) 2. Purchase a Retell Twilio number if you need full SMS integration through Retell's dashboard [(3) ]() I'd recommend testing by sending an outbound SMS from the Retell dashboard—if it shows "sent" but nothing arrives and nothing appears in your Twilio logs, that confirms the limitation applies to your setup. [(1) ]()

​ To learn more, see the sources I considered: [[1] Setup SMS Function Not Saving for Twilio Integration](https://discord.com/channels/1186424376300679209/1446220160213061865) [[2] 2 Way SMS not working?? It won't allow us to choose a number to assign inbound and outbound.](https://discord.com/channels/1186424376300679209/1405373152917454908) [[3] Send & receive SMS](https://docs.retellai.com/deploy/enable-sms) ​

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

### Answer I understand your frustration. Looking back, the official documentation does state that the "Bring Your Own Twilio Number" option exists for SMS setup—you click "Setup SMS Function" in Advanced Add-Ons and provide your Twilio Account SID and Auth Token. [(1) ]() However, the limitation that SMS through Retell's dashboard only fully works with Retell-purchased Twilio numbers (not custom telephony/BYOC) was clarified in community discussions, not prominently in the main docs. [(2) ]() [(3) ]() Your clearest path forward: 1. If you need SMS through Retell's platform: Purchase a Retell Twilio number and go through their A2P application process (business profile → brand → campaign) . [(1) ]() 2. If you want to keep your existing A2P-approved Twilio number: Handle SMS through your own Twilio automation/webhooks instead of Retell's dashboard. Your A2P approval stays valid on Twilio's side. [(2) ]() [(4) ]() I should have flagged the BYOC SMS limitation earlier in our conversation. The documentation presents the "Setup SMS Function" option for BYOC numbers, but community feedback indicates it doesn't reliably work for custom telephony setups. [(2) ]() [(5) ]()

​ To learn more, see the sources I considered: [[1] Send & receive SMS](https://docs.retellai.com/deploy/enable-sms) [[2] Setup SMS Function Not Saving for Twilio Integration](https://discord.com/channels/1186424376300679209/1446220160213061865) [[3] Discord message from @co.abdullah on 2025-12-12](https://discord.com/channels/1186424376300679209/1186462578310910112/1448882948655943680) [[4] Discord message from @mushrooooom on 2025-06-26](https://discord.com/channels/1186424376300679209/1186462578310910112/1387632326682611873) [[5] Phone number can send SMS](https://discord.com/channels/1186424376300679209/1387874084536193024) ​

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