If you wish to know who has called your cellular phone, you can use the paid and free reverse cellular phone lookup services easily available online. In the past there was no directory listing for cell phone numbers. This has changed rapidly with the advent of the internet. You can lookup cell phone number easily using the cell phone directory listing online. You can also find various free reverse cell phone directory websites that you can use. When you make use of the free reverse cell phone services the results can be limited. This is mainly owing to the fact that public cannot access cellular phone numbers. Hence the owner of the website owner has to feed each number manually into the directory. Adding numbers into the site in this way can be really time consuming. You must take up research and find the best cell phone directories for use.