### Answer --- Two-way SMS in Retell AI allows your phone number to both send and receive SMS messages with automated responses from a chat agent [(1) ]() . How it works: 1. Enable SMS capability on your phone number (currently limited to US numbers only) . This requires approval through a business profile, brand registration, and SMS campaign application . 2. Create and attach a chat agent to the phone number . Once attached, the number can automatically receive SMS and reply back to users . 3. Inbound SMS automatically triggers the chat agent to respond . 4. Outbound SMS can be initiated from the dashboard using the "Make an outbound SMS" button or programmatically via the Create Outbound SMS API . For one-way SMS during calls: You can send SMS messages during an active phone call using the Send SMS tool [(2) ]() . This works by configuring SMS content either through a prompt that lets the agent infer the message or using static SMS content with dynamic variable support . Important notes: - SMS capabilities are available for Retell Twilio numbers and your own Twilio numbers (Telnyx is not supported yet) [(1) ]() - Only Retell-issued Twilio numbers support two-way SMS [(3) ]() - The phone number must have SMS capability enabled before setting up two-way conversations [(1) ]() You can also use the inbound webhook to filter and add context to inbound SMS messages .

​ To learn more, see the sources I considered: [[1] Send & receive SMS](https://docs.retellai.com/deploy/enable-sms) [[2] Send SMS](https://docs.retellai.com/build/single-multi-prompt/send-sms) [[3] 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) ​

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

@AI Evy what is the charge of SMS capability

### Answer The SMS capability application process involves the following one-time fees [(1) ]() : **Business Profile**: Free Brand Registration : - Low-volume brand: $4 one-time application fee - Standard brand: $45 one-time application fee **SMS Campaign**: $15 one-time application fee These are application fees charged by the telephony provider for the manual review process, regardless of whether your application is approved or rejected . The sources don't specify ongoing per-message SMS costs or monthly fees specifically for SMS capability beyond the initial application fees.

​ To learn more, see the sources I considered: [[1] 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.