How to Locate a Phone Number Using Facebook. Facebook allows users to show or hide their contact information. If the contact information of the person whose number you're trying to find is unlocked, obtaining his phone number is easy. If the contact information is locked, it will be your contact's decision if you can have his phone number.
Follow the Facebook link in the Resources section below.
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Log into your account, or register for an account if you do not already have one.
Type the name of the user whose information you are trying to obtain into the "Search" field, and then click the search button, which has a small magnifying glass icon on it.
Scroll down the profile screen to the Information area. If the contact information is unlocked, you should immediately see a phone number. In some cases, contact information such as an Instant Messenger screen name or an email address may be included instead of a phone number or physical address.
Send a message through Facebook's messaging system, if a phone number is not available. Request that the contact provide you with her phone number and include your reason for requesting that information. To send the message, click the "Send (person's name) a Message" link.
Compose your message and include a subject header just as you would with email, and then click the "Send" button. Your message will either be accepted or rejected as chosen by the message receiver.