With Android O we get the \"Notification Channels\".
As far as I understand that means that the user can\'t set
That is correct, once a channel is created you cannot make changes to it anymore.
You can't programmatically modify the behavior of a notification channel once it's created and submitted to the notification manager
https://developer.android.com/preview/features/notification-channels.html
What you would have to do delete the channel and create a new one with a different id