Removing persistant "Calls will be made over Wifi" notifications

[dvdmon]

I have my Note 5 set to Wifi-Preferred for calls, but doing so causes persistant notifications "Calls will be made over Wifi." Not one, but two of these. They cannot be swiped away. If I long-press on them, I get the App notifications settings for WfcService. I've tried setting priority to off, Hide on lock screen and Hide content on lock screen to on (this seems to work most of the time) and Previews in pop-ups to off. But the notifications are still visible in the statusbar and when pulling down the notifications tray. Is there any way of getting rid of these?