The person on the other side could be playing a prank on us and make repeated calls. Almost everyone with a cell phone has experienced receiving phone calls from people we do not know.
A reverse cell phone directory is basically a database of name, numbers, and other information. This is the process of locating or discovering the owner of a mysterious phone number. The truth of the matter is that this information is out there, but advertising dollars can only go so far in terms of pushing the boundaries for making information publicly available to everyone.
Their database is created manually and clearly takes a lot of time and manpower, therefore, they don't display results for free. Your information is being bought, sold, and shared between companies and government agencies every day, all the time. You can use reverse information sites when either of these are a problem.
Happy searching. Most of the services will offer you money back guarantees.