Dialing an extension using Google Voice works just like any other phone service: you enter the extension on your dial pad after the call connects. If you're making the call from your computer, you can use the dial pad in the Google Hangouts or Gmail Chat window that appears during the call, or you can use your keyboard's numeric keypad. Depending on where you initiate the Google Voice call, you may experience problems entering the number 4 on the dial pad, but you can easily work around this issue.

Problems Pressing the "4" Key

When you initiate a call directly from the Google Voice website, Google reserves the 4 key for starting and stopping recording. The first time you press the 4 key, the key-press tone sounds just like any other key, but if you press it again right away, nothing happens. This can be a problem when the extension contains more than one 4. The trick is to wait about six seconds before pressing the 4 key again, and then you should be able to enter the extension without any problem. Alternatively, you can make the Google Voice call from Google Hangouts, where the 4 key works normally.