There is no universal toggle for SMS; enabling it requires platform-specific steps for iPhone, Microsoft Teams, RingCentral, or Salesforce.
Trying to enable SMS without picking the right platform first is the most common reason the toggle seems hidden. “Enable SMS” means configuring a carrier fallback on an iPhone, granting permissions in a business phone system, or registering a marketing campaign. This guide shows you exactly where the setting lives on each platform.
For iPhone Users: Enable SMS as an iMessage Fallback
Enabling SMS on an iPhone activates a fallback toggle so the device sends a carrier text message when iMessage is unavailable. Apple’s documentation for setting up Messages details this behavior.
Open Settings > Apps > Messages. Turn on iMessage if it is not already active. Below the iMessage toggle, enable Send as SMS (labeled Retry as Text Message on some older iOS versions). This allows the phone to send a green bubble SMS automatically if iMessage cannot reach the recipient.
Gate: SMS fallback only works with an active cellular plan that supports carrier texting. A data-only plan or an expired line will fail to deliver SMS even with the toggle turned on.
For Microsoft Teams Admins: Enable SMS on a Phone Number
Microsoft Teams allows administrators to enable SMS on specific user phone numbers through the Teams admin center. This is a per-number setting, not a global toggle.
Log in to the Teams admin center. Go to Voice > Phone numbers > Numbers. Select the phone number you want to modify. Click Enable SMS. To disable it later, use the Disable SMS option on the same pane.
Microsoft provides usage reports for SMS activity under Reports & analytics > Usage reports > PSTN and SMS Usage.
Gate: Only a Teams administrator with the correct Voice permissions can enable SMS on a number. The number must be assigned to a user before the option appears.
For RingCentral Users: Complete Brand and Campaign Registration
RingCentral requires approved brand and campaign registration before SMS functionality is enabled for local U.S. and Canada numbers. Toll-free numbers need a separate verification step.
For local numbers, submit a brand registration and a campaign registration through the RingCentral dashboard or API. Once the campaign is approved, link the phone number to that campaign. For toll-free numbers, complete the toll-free verification process. The SMS configuration for an extension can be checked via the GET /restapi/v1.0/account/~/extension/{extensionId}/phone-number/{phoneNumberId}/sms-configuration endpoint.
Gate: SMS will not activate until the campaign is fully approved and the number is successfully linked. Brand registration is mandatory for local numbers in the U.S. and Canada.
| Platform | Where To Enable SMS | Single Most Important Prerequisite |
|---|---|---|
| iPhone | Settings > Apps > Messages > Send as SMS | Active cellular plan with carrier texting |
| Microsoft Teams | Admin Center > Voice > Phone Numbers > Enable SMS | Administrator role and assigned phone number |
| RingCentral | Dashboard / API > Brand & Campaign Registration | Approved campaign linked to the number |
| Salesforce | Permission Set > Send Initial SMS Message to Individual | Messaging enabled in Service Cloud |
| Unitronics | Ladder Software > Use SMS Messaging | Connected GSM modem |
For Salesforce Service Cloud: Grant the SMS Permission Set
Salesforce Digital Engagement relies on permission sets to enable SMS for service users. It is not a simple toggle on a profile.
First, ensure Messaging in Service Cloud is enabled in your org. Create a new Permission Set. Under App Permissions, enable Send Initial SMS Message to Individual. Assign this permission set to the users who need to send SMS from the console.
Gate: The user must also have the standard messaging permissions assigned. SMS will not work if Messaging in Service Cloud is turned off at the org level.
For Unitronics PLCs: Configure the GSM Modem
Unitronics PLCs require a connected GSM modem and a software toggle to enable SMS messaging. This is an industrial application, not a consumer phone setting.
Connect the GSM modem to the controller. Open the controller software and select Use SMS Messaging. This turns on system bit SB 180, Initialize GSM Modem, at power-up. The default modem settings are 19200 baud, 8 data bits, no parity, 1 stop bit.
Gate: A modem PIN code may be required. Access can be restricted to numbers saved in the SMS phone book.
Why Is SMS Not Working?
Enabling the wrong setting is the most common cause of failure. The confusion usually comes from mixing up iMessage with SMS, or assuming an admin panel toggle is enough when carrier registration is required.
| Mistake | What Actually Happens | How To Fix It |
|---|---|---|
| Only iMessage is turned on | Messages stay blue and never send a green carrier SMS | Enable Send as SMS in iPhone Messages settings |
| SMS enabled in Teams without an assigned number | The Enable SMS button is grayed out | Assign a phone number to the user first |
| RingCentral campaign not approved | SMS fails silently or returns an error | Check campaign status in the RingCentral dashboard |
| Salesforce user lacks permission set | SMS button is missing in the console | Assign the Send Initial SMS Message to Individual permission |
| Unitronics modem not connected | SB 180 stays off and no SMS is sent | Verify GSM modem is powered and communicating |
SMS Compliance: Opt-In and Opt-Out
For business SMS broadcasts, collecting explicit opt-in and honoring STOP replies is legally required in the U.S. and Canada. Include opt-in confirmation with message frequency and standard carrier disclaimer language stating that message and data rates may apply.
The final checklist for enabling SMS across any platform is the same: identify the exact platform, check the prerequisite, and apply the specific setting or registration listed here. That sequence eliminates the guesswork and gets the message through.
References & Sources
- Apple. “Set up Messages on iPhone.” Official guide for iMessage and SMS fallback settings.
- Microsoft. “Manage SMS for Microsoft Teams.” Documentation for enabling SMS on user phone numbers in the admin center.
- RingCentral. “SMS Requirements.” Describes brand registration and toll-free verification for SMS.
- Salesforce. “Set Up Digital Engagement.” Steps to enable SMS permission sets in Service Cloud.
- Unitronics. “Configuring SMS Messaging Features.” Knowledge base for GSM modem setup and SB 180 activation.