Then I don't know what you can do if notifications are not disabled for "Dialer & Contacts" app...
Probably, irrelevant here, but maybe not..
Try this:
Settings-> Privacy Protection -> Special Permissions -> Battery optimization -> Hit the 'Not Optimized' blueISH banner on the top, change to All apps, now search for Notifications app, click on it and change from Optimized to Not optimized..
Reboot your phone.
As a side note, I'm still debugging these notifications issues on Global & EEA ROMs, and while we started from It may not work on WIFI ( or it is buggy ), we figured there may be more than one bug and may affect any ROM, depending on usage and region.
One workaround we found is working is the one I described, however, it may not work for any app or any phone.
There exist a second one, which is basically just sh***y and you may not get the notification but see something is trying to
notify you. That would be to tick on the 'Wake display on notification' option.
One more thing, we noticed, is some apps do not enable *sounds* notifications on installation, the reason is unknown right now. So you may also check that too.
In any way be sure you enable Notifications badges for at least apps you notice are buggy regarding that, so you can see at least you have a notification in those apps.
