If you are having issues receiving calls (calls go straight to voicemail), you may find the following article helpful:
I had that problem too, but noticed I always got calls from my Favorites but others went straight to voicemail. Even though Do Not Disturb was not turned on, it seems that changing the Do Not Disturb setting to Allow Calls from Everyone has fixed this issue for me. Prior it was set to Allow Calls from Favorites. It is odd that it is enforcing this rule even when DND is turned off, but that is what happened to me.