This is happening on a OnePlus 3T running OxygenOS 5.0 (Android 8.0.0) on the GSM network.
After deleting a message in visual voicemail, it keeps reappearing a short time later, along with a system notification that I have a new voicemail. I must have deleted the thing half a dozen or more times over the past couple days, but it just won't stay dead.
I didn't experience this behavior prior to my update to Oreo, and I'm not sure if this behavior is rooted in a phone OS issue (not properly initiating a message deletion on the server), or some sort of server-side voicemail issue.
Thanks in advance for any feedback on this.