You can make a return call to someone who has left you a voicemail message.
To make a return call from voicemail:
1. Using the 
Messages gadget on the Main tab, locate the message from the person that you want to callback.
2. Click on the name or number details of the caller to make a return call.
•The progress of the call is displayed on a tab in the 
Calls gadget. If the call fails, the gadget displays a reason for the failure if known.
•When calling an internal user, if they do not answer you can set a ringback to call you when they end their current or next call.