There are many different kinds of phone searches available for your use online. Though some callers who will not or do not identify themselves are harmless, you won't know that until you know who they are.
Trying to find a reverse cell phone directory is much easier these days then people think. You will not find information on these when you use reverse white pages, as these listings are for landline numbers only. You can search by name, just enter the first name or first name initial, the last name or last name initial, the city or zip code, and the state.
It takes a lot of money and time intensive work to buy cell phone records from all the service providers, and crosscheck them to make sure they are up-to-date. That's why you'll have to make a small investment to get access to other people's cell phone records. Whatever number you may have, you can always try this site for a reverse number service.
Most of the services will offer you money back guarantees. Cell numbers are typically harder to track down and you won't find them in a free service.