The call to action (opt-in/out compliance requirements) needs to be compliant and include the following components:
Organization or individual being represented in the initial message
Service delivery frequency or recurring messages disclosure
Customer care information (typically "Text HELP for help" or Help at XXX-XXX-XXXX) - not required for single message programs (i.e 2FA)
Opt-out instructions (typically "Text Remove to cancel")
Link to Privacy Policy describing how end-user opt-in information will be used
Link to Terms and Conditions describing terms of service
Incorporate a checkbox option that end-users must select in order to receive SMS messaging. The checkbox can not be pre-selected. The checkbox provides the end-user the ability to agree, or not agree to receive SMS messaging.
Example of Opt-In Verbiage for your Website:
By clicking submit, you are providing express consent to be contacted by SMS, possibly using automated technology to the number you provided. If at any time you wish to opt-out of communication, please reply "STOP" to cancel. Text "HELP" for help. Message frequency may vary. Message/data rates may apply. Submission of this form does not authorize the purchase of goods, services, or products. See the privacy policy/Terms and Conditions on the webpage.
To check out more information, please visit Twilio’s Support Article on SMS & Compliance: https://support.twilio.com/hc/en-us/articles/4408675845019-SMS-Compliance-and-A2P-10DLC-in-the-US