Anonymous call rejection
- The codes described are relevant only to the NANP telephone system. A similar feature is used in European ISDN networks, which is mandated by the European Telecommunication Regulation in the Directive on Privacy and Electronic Communications, cf. Wikipedia (de).
Anonymous call rejection is a landline calling feature which screens out calls from callers who have blocked their Caller ID information. Anonymous Call Rejection is based on caller ID (not automatic number identification or ANI). It is often free with caller ID on landlines.
Incoming callers with caller-ID blocking enabled, when ringing a line with anonymous call rejection, will hear a message stating that this line does not accept calls from callers who block their number. Callers who have blocked their Caller ID information will then hear a recording instructing them not to block their Caller ID when calling that line. This feature is normally included with Caller ID, but may be available separately from your local telephone company. The ACR feature is not available in all areas. It is not available from most cellphone services with caller ID, such as Sprint, T-Mobile USA or AT&T. Verizon Wireless does provide this service, but ACR prevents dialing a feature code or successfully calling customer service. Verizon Wireless does not currently provide blocked or anonymous call rejection, but customers may block up to five specific numbers at MyVerizon.
How to use
Where available in North America, one may enter *77 to enable, or *87 to disable, anonymous call rejection.
Resulting error message
"The number you are calling does not accept calls from callers who do not allow the delivery of their telephone number. Please unblock your number and try again."
"We are sorry private calls are not accepted by this number. To complete your call, hang up and press *82 on touch tone phones, or dial 1182 on rotary phones; then re-dial the number." "If you have caller ID, your name and number may be displayed to the recipient of the call."
"We're sorry; the party you have reached is not accepting private calls. If you want to allow your number to be displayed, hang up, dial *82 or 1182 from rotary phones, and redial the number."
"We're sorry. The person you are calling does not wish to talk with callers who block their number. If you wish to reach this person, please hang up, and place your call again, without blocking your number."
And in the United Kingdom the standard message with BT is:
"The person you are calling is not accepting anonymous calls. Please redial without withholding your number."
Service usage messages
"Your anonymous call rejection service is now on. Callers who block their number will get a recording saying you do not accept blocked calls." 
"Your anonymous call rejection service is now off. Callers who block their number can now reach you." 
- iobi, a call management service by Verizon (pronounced "eye-oh-bee")
- Pat Fleet, the voice behind the rejection message
- Vertical service code