Thanks for taking the time to post to our community! Is this something that just started by chance or has it always been this way? It sounds like the network is not syncing properly when you check the VM and that is something that we would need to get refreshed for you. If you have a moment, please give our folks over the phone a call so we can get a support ticket opened for this issue.
I have a new Galaxy S10 that's doing the same. Apparently the only way to clear it is to dial voicemail & listen after I've already listened to visual voicemail. Very annoying, it kinda makes visual voicemail worthless.