To call a colleague's extension from inside the same company, dial the extension digits on your phone and press call. Outside callers reach the same extension by dialing the company's main number and entering the extension when the greeting or menu asks for it.
Extensions let a company have one public number and many internal lines. Each person or department gets a short number that rings their desk phone. The main number is the one printed on the website or the business card. The extension is what gets the call to the right person once it arrives.
Calling a colleague inside the company
On most business phone systems, a colleague's extension can be dialed by itself. There's no need to add an area code or the full phone number. The call stays inside the company's phone system. The phone you're using has to be connected to that system, such as a desk phone. A phone that is not connected to the system won't reach an internal extension.
Calling a company from outside
A caller outside the company usually reaches an extension in one of two ways. They can dial the direct extension if it has been shared with them. More often, they dial the main number, listen to the greeting or menu, and then enter the extension when asked. Some systems ask for the # key after the digits. The exact steps depend on how the company's phone system was set up, so the greeting itself is the best guide.
Some phones also let you save a pause after a main number, so the extension is sent automatically when the call connects. This is a feature of the phone, not the phone system, and the pause length varies by device.
When an extension doesn't answer
A call to an extension can go to voicemail, another phone, or a call queue, depending on how the administrator set it up. If a colleague's extension rings nowhere, the cause is usually a forwarding rule, a closed line, or a device that is not registered. The fastest check is with the phone administrator, who can see the call's routing. For how queues work, see call queue management. For voicemail behavior, see what business voicemail is.
When to check with your administrator
Ask the administrator if an extension rings nowhere, if the same extension behaves differently from one office to another, or if outside callers hear a menu that does not match the company's list of departments.
For the basics of how a business phone system is organized, see what a business phone system is. For why many extensions sit behind one main number, see what a DID number is.
