When the phone rings and the caller ID reads "blocked" or "unknown," you don't know who it is or whether to answer the call. An anonymous caller may be a telemarketer or a friend playing a prank on you, but, regardless of the reason for the anonymous call, there are a few steps you can take to track down your caller. These steps do not work all of the time, but they provide a thorough and effective way to try to track down your anonymous caller.
Dial *69 in order to call the number of the person who just called you. Most major cellphone providers have this function, and it may or may not cost a slight fee. When you call back, you can explain that you received the call and didn't know the identity of the caller, or wait to see if a voicemail picks up that reveals additional information.
Use a phone software program to trace and record incoming calls. Many companies offer a program that reveals blocked and restricted calls as well as blacklisted callers on your caller ID, and records incoming calls.
Look up the phone number using an online search engine. This won't work with anonymous calls that do not reveal phone numbers, but many anonymous calls reveal the phone numbers and no further information. You can plug the entire phone number or area code into a search engine, such as Google or Yahoo, in order to see if the number belongs to a company, person or location.
Wait and do not answer the phone, allowing your voice mail to pick up the call. If the caller leaves a message, you can gain insight as to the identity of the caller. In addition, sometimes callers have to enter a phone number to leave a voice mail, in which case you can look for the number in a search engine.
Contact law enforcement agencies and have them trace the call for you. In some cases where you feel endangered, law enforcement officers can intervene and track a call.
If you keep receiving anonymous calls and would like them to stop, some cellphone companies offer anonymous call blocking in which you can block all numbers that do not reveal information on caller ID.