Dial *67, then the full 10-digit number (no spaces or dashes)
On some carriers, dial #31#, then the full 10-digit number (caller ID blocking per call)
Use your phone’s caller ID settings:
iPhone: Settings → Phone → Show Caller ID → toggle off
Android: Phone app → Settings → Calls → Additional settings → Caller ID → Hide number
If available, enable “Block Caller ID” in your carrier’s account settings
Use a VoIP app with “Hide caller ID” enabled (if supported)