Here comes, again, the annoying words "cellular carrier" on your caller ID. And for the nth time, you don't know whether to answer it or not in fear of hearing a telemarketing agent on the other end trying to sell you their latest products. What other word can best describe your agitation? You could now be probably cursing someone for inventing cell phones without you knowing who's calling you. But remember, every complication has a solution. Leave it to reverse phone number lookup service providers.
Most providers offer their services with no charge for regular phone numbers (like landlines) lookups since directories are found on public domains and other listings unless the user opted not be listed in any. After a number of times trying to lookup for a mobile user, you'll get to realize that you have to pay for it. Reason is cell phone users have the option on whether their names be listed on public domains or not. Who won't want privacy if it's one of your options? None I guess. Databases that contain up to date and accurate contact information of mobile account holders are provided by cell phone companies for a fee. They just mean business.
Aside from the exact answer to your question of who might be calling you, reverse phone lookup service providers also give you details on the historical background of the number (who might have previously owned the number and stuff). Nominal fee which will cover unlimited searches for a year is a no-brainer if satisfies your need of tracking down a person using their cell phone numbers. Your 24 hours of searching for someone using free directories is just a matter of seconds for paid services.