If an unknown number is causing you a bit of grief, your first thought might be to find out who is on the other end of the line. Free white pages are available to everyone who uses the web.
If you think you'll be using the directory frequently, just add it to your favorites and you'll be able to head there directly from then on. Traditional examples of directories are deeply ingrained in us. The information returned to you will give you person's name, current address, location, their phone carrier, criminal histories, court records, legal files, birth record and much more.
The paid services online offer larger databases than the free ones. Some reverse phone number directories boast of a huge database for a very low fee, but once you pay, you realize that their database is nothing else but links to other sites, which charge you again. This may give you the best results, but you can try many more different reverse lookup services as well.
If you do not get results, you can get refunded by the reverse cell phone lookup service. It is the sad truth that the only place where you are likely to find detailed reverse cell records is within the legitimate paid directories.