Voicemails are usually received as attachments that won't let you listen to them. You have to download the VM file first, then open the file and play it separately. This flow/PA captures the VM email when it hits your inbox, creates a new email with a link to play your VM in a browser, and deletes the old VM to your deleted folder. All I have to do to listen to my VM now is click the link. Saves time, local disk space, and frustration.
The voicemails do collect in a folder called \voicemails in your Onedrive, so you should occasionally clean out those files to conserve disk space online.