f you want to Remove mobile number From Facebook account, you must watch this video or follow this steps:
1- Open your Browser
2- Open www.Facebook.com
3- login using your details.
4- On the homepage of your profile, Click Drop-down arrow
5- From the drop-down list that appears, click the Settings option.
6- Select Mobile from the categories present in the left pane.
7- behind the phone number you want to delete it, Click on Remove
8- it will display a confirmation message asking if you really want to delete this phone number from your Facebook account Click on Remove Phone
9- then you will be required to enter your Facebook password for security purposes.
10- Type your password and click Submit After this, your phone number will be deleted from your Facebook