How Spam Blocker Apps Work
They check incoming numbers against a database and warn you if a number has been reported as spam or scam.
Popular Options
Whoscall (free/paid, large global database), Denwa-cho Navi (free, Japan-focused), and carrier apps (220-330 yen/month, network-level blocking). App databases and pricing plans are updated frequently, so check the app store for the latest plan details.
Choosing Tips
Check database size, privacy policy (apps may send your call history to their servers), and battery impact. Carrier services are most reliable but cost money.
No-App Alternatives
iPhone's "Silence Unknown Callers," Android's "Block unknown callers," and simply letting unknown calls go to voicemail.