Call rejection automatically blocks incoming calls from specific numbers or withheld numbers, preventing the phone from ringing. It's the most fundamental defense against nuisance calls and telemarketing, available on both smartphones and landlines.
On smartphones, call rejection uses built-in features. iPhone users tap "Block this Caller" from call history; Android users select "Block." Blocked callers hear a busy tone or get disconnected. SMS from blocked numbers is typically also filtered.
For landlines, NTT's "Nuisance Call Blocking Service" (660 yen/month) is standard. After receiving an unwanted call, a dial operation registers the number, and future calls from it hear an automated rejection message. Up to 30 numbers can be registered. Alternatively, phones with built-in call blocking features are available.
Blanket rejection of withheld calls is also effective. NTT's Number Request service asks anonymous callers to redial with caller ID enabled. Legitimate callers will comply, efficiently filtering out nuisance calls.
However, call rejection has limits. Callers who change numbers or use caller ID spoofing can bypass individual blocks. In such cases, consider spam filter apps or consulting the police.