Send & receive SMS

A step by step guide to send & receive one way & two way SMS

Communication is not bound to voice only. SMS is a common way to communicate with customers. This guide will show you how to enable SMS with Retell Twilio numbers or bring your own Twilio number.

SMS capabilities are available for Retell Twilio numbers and your own Twilio numbers. Telnyx is not supported yet. For other custom telephony providers, please check your own telephony provider’s documentation on how to enable SMS.

Current SMS capabilities are limited to US numbers only.

Enable SMS capabilities

This step is a prerequisite for sending one way SMS during call and setting up 2 way SMS conversation.

Option 1: Enable SMS for Retell Twilio Numbers

To enable SMS, it will go through the following application and approval steps:

• Get approved for a business profile (free)
• Get approved for the brand based on business profile ($4 one time application fee for low-volume, $45 one time application fee for standard)
• Get approved for a SMS campaign ($15 one time application fee)

It can take around 2-3 weeks for the entire application, sometimes longer, as it’s a manual review process on the telephony provider side. We will notify you via email when the application is approved or rejected with the reason. If your application is stuck in pending review for over a month, please reach out to support and we will help escalate.

Detailed steps

1. Get approved for a business profile

   You can reuse an existing business profile or create a new one here. Follow the instructions at Business Profile to get approved for a business profile.

2. Select a brand type and get approved for the brand

   Only one brand can be created per business profile and it cannot be changed once created. If you need to change the brand type, you have to create a new business profile.

   Here you get to select two types of brands:

   • Low-volume:
     • $4 one time application fee
     • send fewer than 6,000 message segments per day to the US (2,000 message segments per day to T-Mobile)
   • Standard:
     • $45 one time application fee
     • SMS limit may fall between 6,000 and 400,000 message segments per day to the US (2,000 - 200,000 per day to T-Mobile)

   Depending on your company’s type, you might be asked to fill out additional information.

3. Get approved for a SMS campaign

   

   Here you will fill out the use case, and sample messages you intend to send. Please note that there’s very strict rules on SMS, and if your actual traffic doesn’t match the sample messages, your number / telephony subaccount might be suspended. Therefore, please be honest and provide answers that match your intended use case. If you ever need to send different SMS messages, you can create a new campaign (check FAQ for more details).

Rejected application FAQ

What are some of the common reasons for application rejection?

There are a few common reasons for application rejection:

• the campaign application did not provide detailed information on the use case and sample messages.
• Opt in workflow was not explained clearly.
• Business profile or brand was not approved, due to missing or incorrect business information.

Feel free to read more at Twilio’s A2P 10DLC documentation.

If my application is rejected, what should I do?

Please check the rejection reason and update your application accordingly. If you are rejected at a later stage, you might be able to reuse the previous steps. For example, if your business profile and brand are approved, but the SMS campaign is rejected, you can reuse the business profile and brand approval, and create a new SMS campaign application.

If my application is rejected, will I get a refund?

No, you will not get a refund, as the charge is for the telephony provider’s manual review process, and that will be charged regardless of the application outcome.

How to create a new SMS campaign if I want to change my use case for the number?

You can delete the SMS capability on the number (this will not delete your approved business profile and brand, and campaign, those can still be reused), and create a new SMS application with a new campaign while reusing the business profile and brand.

Option 2: Bring Your Own Twilio Number

If you already have a Twilio number with SMS capabilities enabled, you can integrate it with Retell by following these steps:

1. Click on Setup SMS Function in Advanced Add-Ons

   Navigate to your phone number settings in the Retell dashboard and click on the “Setup SMS Function” button under Advanced Add-Ons.

2. Provide Your Twilio Credentials

   Enter the following information from your Twilio account:

   • Account SID: Your unique Twilio Account identifier
   • Twilio Auth Token: Your Twilio authentication token for API access

   You can find these credentials in your Twilio Console under Account Info.
3. Configure SMS Settings

   Once your credentials are verified, your Twilio number will be integrated with Retell’s SMS capabilities. You can then use it for:

   • Sending one-way SMS during calls
   • Setting up two-way SMS conversations (requires enabling useInboundWebhookOnNumberCalled)

• Make sure your Twilio number already has SMS capabilities enabled and is compliant with SMS regulations before integration
• To enable two-way SMS conversations, enable the useInboundWebhookOnNumberCalled option in your phone number configuration
• For more information about A2P 10DLC compliance, see Twilio’s A2P 10DLC documentation

Send one way SMS during call

Refer to following documents for more details:

• For Conversation Flow: SMS Node.
• For Single/Multi Prompt: Send SMS.

Set up two way SMS conversation

Once your SMS capability is enabled for the number, you can set up a two way SMS conversation by attaching chat agents to the number, where the number will be able to receive SMS and reply back to user.

Once the chat agent is attached, the inbound will already work. Inbound webhook can be used to filter and add context to inbound SMS. Read more at Inbound Webhook.

For making outbound SMS, you can do that in the dashboard by clicking on the Make an outbound SMS button, or use the Create Outbound SMS API to programmatically send it.