Use a reverse phone lookup service if the number is revealed later
Check your phone carrier’s call logs or spam protection app
Enable call tracing through your carrier if the calls are harassing
Ask your carrier about anonymous call rejection or caller ID unmasking options
Use a third-party call blocker or call identification app
Let the call go to voicemail and listen for clues
Save the date, time, and frequency of the calls
Report repeated harassment to your carrier
File a police report if the calls are threatening or abusive
Contact your local telecom regulator for anonymous call complaint procedures