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

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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)

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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).

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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

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FAQ