Contact your phone carrier and ask about call tracing or anonymous call tracing services
Use your phone’s built-in spam and call-blocking features to log repeated unknown calls
Enable call logs and save the date, time, and frequency of each No Caller ID call
Ask the caller to leave a voicemail, which may reveal a number or identity
Use a call-tracing service if your carrier offers one, such as dialing a trace code after the call
Report harassing or threatening calls to local law enforcement
File a complaint with your carrier if the calls are persistent or abusive
Use a third-party call-blocking app that can identify or filter hidden numbers
If the calls are illegal or threatening, request a subpoena through law enforcement for carrier records
Keep records of all calls, voicemails, and any related messages