To stop Facebook notifications from being sent to your phone, you can simply text "Off" (without quotation marks) to the number
that you send your status updates to. Alternatively, you can go to the Mobile tab
of your Account Settings page and change your settings to "Off." Note that you can still send text messages to the same number to update your status or take actions Facebook.
You can also choose to completely remove a number from your account on this page by clicking "remove" next to the phone number that you wish to remove.