First, check the Mobile page for more information about whether your carrier is supported. Your carrier is supported if it is listed in the drop-down menu that appears when you click "Sign Up for Facebook Text Messages."
If your carrier is not supported, we encourage you to contact your carrier to let them know that you are interested in this service. If enough people show interest, they may decide to support our Mobile Texts feature. For now, please note that you can use our Mobile Uploads feature to upload photos, videos, and notes directly from your phone. You should also be able to access your account via Mobile Web at m.facebook.com or iphone.facebook.com for iPhones.
If your carrier is supported, please read the following guidelines to troubleshoot your problem:
Be sure you are sending your text to the correct number for your carrier.
Make sure that your phone does not include a signature at the end of your text messages. This can interfere with Facebook Mobile correspondence.
Try sending "On" (without quotes) instead of "f" to receive your code.
If you have recently ported your number from a different carrier, you may not be able to receive the confirmation code to activate Mobile Texts. This is a problem that we are aware of and hope to resolve it as soon as possible. We apologize for any inconvenience.
If none of the above information resolves your issue, please click here to submit a report about your issue.