Nobody wants to hear busy signals on a business call.
Nor does anyone want to sit through several rings and get no answer when they call a business. Thus voicemail is a necessity for any company. The typical system is like a bunch of answering machines put together. Each user can pick up personal, private messages, usually by keying in a numeric password. A computerized greeting can be used or a personal one can be recorded, telling the recipient that you are out, that you might be reached another way and to leave a message if needed.