Call blocking features on personal phones, the National Do Not Call Registry and phone block services from phone providers are three ways to activate call blocking. These services block calls through several methods, including by numbers listed in databases, activation buttons on personal phones and call rejection features sold separately.
Some phones or phone plans have call blocking features with which users can program lists of numbers to block. There are also specialized plans that target specific numbers, such as CenturyLink's Anonymous Call Rejection, which blocks anonymous and private numbers.
AT&T also provides an online method of blocking unwanted callers. The customer blocks calls by logging in to a personal AT&T account and turning on the Call Blocking feature within the account's Manage Features section. The customer can add up to 20 numbers to the block list. The customer then presses "*60#" on the phone to turn on call blocking and can turn the feature off by pressing "*80#".
The National Do Not Call Registry blocks unwanted phone calls by placing individuals on a national list of those who do not want to receive unsolicited phone calls. The National Do Not Call Registry website allows interested users to put their names on the list for free and issue complaints for violations. Sellers and telemarketers have access to the list. The list does not apply to tax-exempt non-profit organizations or businesses with which the persons on the list have established business relationships.