Right now the only way you are able to perform a reverse phone lookup is by paying a small nominal fee to get access to the huge database. It is a huge database that includes numbers such as cell phone numbers, unlisted numbers and even landline telephone numbers as well.
The reverse phone search companies spent a lot of money in order to get access to this large database that you now can have access to. One of the reasons that reverse phone search companies are charging a small nominal fee is because of privacy reasons. The cell numbers look up companies are bound by agreements with major telephone companies and mobile companies to not give out such private information out of the public for free.