To trace phone calls from an unavailable number in the United States, dial *57 after hanging up, and follow the directions provided by the electronic voice. Report the number after three successful traces by contacting your phone service provider's annoyance call department. Alternatively, search for online tools that are capable of locating unknown numbers by typing "anonymous call tracing" on a search engine.
Try dialing *69 to call back the anonymous caller, and ask him about his identity or wait for a voicemail to discover information about the caller. This option may incur a fee depending on the service provider. You may also download a phone software designed to locate and record incoming calls. This type of software lets you know about blocked calls, restricted calls and blacklisted callers.
File a complaint at a local police station if the caller keeps harassing you, as service providers usually require a police report before investigating annoyance calls. Contact the phone company to find out about its particular policy regarding annoyance calls.
Before filing a police report, prepare useful information, especially the time of the calls, the caller's messages and any background noise. Provide details about distinct characteristics based on the caller's voice, such as intoxication or a speech impediment. To prevent unwanted calls, call your service provider to request the activation of a block against anonymous callers.