If you want to find out who's behind a phone number, you have a few options for doing so. A number of websites offer reverse look-up searches by phone number. However, most of them are not "original" -- i.e., they redirect you to another site with the results or they say they are free but after you search, you are given "payment options." Some free original websites do exist for this job, including anywho.com, whitepages.com and people.yahoo.com.
Visit anywho.com. Click the "By Phone Number" link. Enter the phone number, including area code and separated by dashes. Click "Find."
Navigate to whitepages.com. Enter the phone number, with area code and dashes, in the Reverse Phone field and click "Find."
Go to people.yahoo.com and enter the phone number in the Reverse Phone # section following the example. Click "Search."