In the visual voicemail window in the WebEx mobile app, there is no option to simply forward a voicemail like there is in Jabber. I found the following in the deployment guide:
"Users get a visual voicemail inbox in Webex App. They can play messages, delete messages, mark as read, and respond with an audio or video call:
Users can also click Call Voicemail , which accesses the voicemail system with an internal or external call. Users can then retrieve, listen to, reply to, forward, and delete their messages."