In the past, when you call an office building or business, you would either be transferred to the department you want to talk to, or given their extension number. This extension is usually a 2-3 digit code that when dialed, transfers you automatically to the particular person or department you want to speak with. The reason why this code works is because it is programmed into a PBX system.
The service that most owners look for is VoIP or voice over internet protocol. This service allows the user to make long distance calls using the standard internet connection