Call Forwarding No Answer forwards your calls to a pre-programmed number such as an answering service whenever you do not answer your phone after a set number of rings, which is pre-programmed between two and seven rings.

You can have this service in conjunction with regular call forwarding, but when call forwarding is in effect it overrides Call Forwarding No Answer.

You can NOT combine this service with voice mail service.

Normally you can not change the forwarding number or the number of rings to wait at will.   You may only change the number by calling the phone company and requesting that the number be changed.   This sometimes can take up to 24 hours.

Some telephone companies, especially VoIP providers allow users to manipulate the forwarding number and number of rings through a web portal.