What is the Optus Voicemail Number? Moose Support January 18, 2018 07:36 Updated Follow The Optus Voicemail number is 321. To set up your voicemail dial 321 from the handset and listen to the prompts. Related articles I requested not to have Voice Mail how do I turn it back on? How do I remove Voicemail and Missed Call Service? How do I make my phone ring longer before it goes to Voicemail? How to set up MMS APN settings for Moose Mobile? How do I activate Call Hold Call Wait? Comments 0 comments Please sign in to leave a comment.