Hi,
Thanks for writing in! Here are some common SMS troubleshooting tips:
• Experiencing a delay in receiving Twitter SMS updates to your phone? This is most often due to heavy traffic on your carrier's network. Don't worry, things should be back to normal shortly!
• If you're receiving updates from an unknown account, you can reply to the SMS with the word STOP, twice. This will remove your phone number from the account in question.
• Having trouble adding your device to your account? We recommend trying web activation. Follow the steps in this article to learn how: https://support.twitter.com/articles/110250-adding-your-mobile-number-to-your-account-via-web
• Need to reset your password? Check this article for more information: https://support.twitter.com/articles/14663-recovering-a-lost-or-forgotten-password
• Not sure if you're using a supported carrier? We keep an up-to-date list of carriers and their short codes here: https://support.twitter.com/articles/20170024
• If your carrier is not supported, you can use a long code instead: https://support.twitter.com/articles/14226
We hope that helps! If you're experiencing an issue not listed here, please reply with further details and we'll take a look.