How to Take Your Number Off of Facebookby Lara Webster
Posting your phone number to your Facebook profile makes it easy for your confirmed friends to contact you. If you want to protect your privacy, however, taking your number down from the site is a piece of cake. If you provide your phone number to the people at Facebook, the site can send you updates when you receive certain notifications, such as a new post to your wall. Remove your phone number if it changes or you don't want to get mobile alerts.
Remove your number from the Facebook mobile service by clicking on the "Account" link at the top of Facebook and choosing "Account Settings" from the drop-down menu.
Click the "Mobile" tab.
Click the "Remove" link immediately to the right of your phone number in the "Mobile Phones" section of the page. Scroll down and click the "Save Preferences" button at the bottom of the page.
Remove your phone number from your profile by clicking "Edit Profile" in the top right corner of your personal profile.
Click the "Contact Information" tab in the left column of the screen. Highlight your phone number and press "Delete." Scroll down and click the "Save Changes" button.