The Digium Phone Voicemail App lets you screen a voicemail message as it is being left, answer the call immediately, or let the call go to voicemail. By default, all extensions have permission to use voicemail screening. However, the admin can turn this off in extension management.
How it works:
When a caller is leaving you a message both the message waiting indicator and your line key blink in amber, and there is a recording icon in the main screen's title bar. To access the Screening option, press the Msgs button. This displays the App's softkeys: Screen, Answer, Folder, and Refresh.
Press Screen to listen to voicemail as it is being left. This displays the voicemail screening information.
Press Answer either before screening or while screening to connect to the caller and end the message in your mailbox. The active message, the one being left by the caller, is displayed at the top of the voicemail list.