How long ago did you do this, and has the notification come back? I've been able to get it to go away for only an hour or two. Before I hard reset my phone I'd like to know if it is still working for you.
I've discussed the issue with Sprint, the tech told me they are getting tons of calls with the same exact issue. (5 new notifications). We went through a bunch of steps. I even had him activate an old phone, then reactivate the S5, didn't work.
On my own, I even froze both VM apps with Rom Toolbox, didn't work. I uninstalled both apps, didn't work. I deleted both apps, didn't work.
Even Gravity Box which has an ongoing notification blocker feature doesn't recognize the notification.
The only thing that temporarily fixes the issue is long pressing the notification, selecting app info, and either force closing or clearing the data of the phone app. I hope this gets resolved soon.
Thanks!
Carrier: Sprint
Model: Galaxy S5