How do I reject calls from people that withhold their number?
The main reason people want to do this is to avoid telemarketeers, who typically withhold their number. British phone users have some protection as they can opt out from receiving such calls using the Telephone Preference Service. Under The Telecommunications (Data Protection and Privacy) (Direct Marketing) Regulations 1998 it is now an offence punishable by £5000 fines to cold call anyone registered with the TPS, so before you do anything more complicated, register with the TPS, or the fax equivalent. This was brought in as a result of Brussels’ Telecoms Protection Directive (see below), so most EU countries should have something similar – even if you haven’t registered yet, pretending that you have should get the cold callers sweating
Answer from the Caller ID FAQ: http://www.ainslie.org.uk/callerid.htm (Copyright 1998-9 Alastair Ainslie) Americans have had Automatic Call Rejection (ACR, also known as “block blocking”) for several years. Bell Atlantic have a sophisticated exchange-based ACR that includes a PIN that you can give out to friends who would otherwise be rejected (see press release). With ACR, any call that has a Caller ID of “WITHHELD” is automatically ignored. Calls that present as “UNAVAILABLE” (e.g. from a handful of older exchanges) or “INTERNATIONAL”, “PAYPHONE” or whatever are allowed through. This is great for those suffering from nuisance calls of all kinds, less good for telesalesmen and other phone pests. However, “UNAVAILABLE” seems to be the default for some switchboards; once ACR becomes widespread companies will find they have to configure their switchboards correctly if they are to communicate with all their customers. (I’m no expert on switchboards, but the impression I get from uk.teleco
