Voicemail Notifications on Galaxy S9+

Hi. I've had a Samsung Galaxy S9+ on Xfinity Mobile for nearly a year and voicemail notifications have never worked. All settings on the phone are correct (notifications and app badges are enabled). I've tried resetting network settings. Google Support says I need to have Xfinity Mobile change me over to Basic Voicemail. I've spent 2 hours on the phone with support and they just don't get it. Any help would be appreciated...