Agreed - DND makes it so you do not receive any phone calls, notifications, or any notice while it is active. You can enable certain settings like allow a call if they are in your contacts, or they call multiple times.
Right now, even with DND on, you still receive calls from RingCentral at full volume. It completely ignores the setting, making the setting useless. This is very frustrating as receiving calls at 3am even with DND on is not fun!