Call blocking is a feature that automatically blocks incoming calls matching specific phone numbers or conditions. As one of the most basic and immediately effective nuisance call countermeasures, it can be configured at three levels: device, carrier, and app.
In smartphone device settings, specific numbers can be individually blocked from call history or contacts. Both iPhone and Android offer an option in the phone app to block the selected number (the label and its location vary by model and OS version). Blocked numbers won't ring, and callers hear a busy tone or announcement.
Carrier services include Docomo's "Nuisance Call Stop Service," au's "Nuisance Call Rejection Service," and SoftBank's "Number Block." Whether they are free, how many numbers can be registered, and whether you need to apply differ by carrier and plan, so check with your provider. Unlike device settings, these block at the network level, remaining effective even when the device is powered off.
For landlines, NTT East/West's "Nuisance Call Rejection Service" is available. Registering the most recent incoming number causes subsequent calls from that number to hear a message saying the call cannot be accepted, then disconnect automatically. On Hikari Denwa the equivalent feature is offered as the "Nuisance Call Rejection List," priced by NTT East at 220 yen per list per month including tax as of August 2026. The number of entries allowed differs by line and service, so check with your provider before subscribing. Many phone models also have built-in call blocking features, and combined with Number Display, can blanket-reject anonymous or unregistered numbers.
Third-party spam call filter apps (Whoscall, Denwa-cho Navi, etc.) can warn you about numbers suspected of being nuisance calls and automatically reject calls that match your settings. The features offered vary by app and plan. See how to fight nuisance calls for call blocking procedures and where to report.