do not disturb mode

First go to the do not disturb settings and see that the switch is green for do not disturb. If it is on a schedule, then it would not be green until it is the start time. If you scroll down, you will see an option for silence. To not make it sound at all, select "always". Then change the allow contacts to no one or make a few exceptions if you want. If you already done all of things and there is still an issue, then I wouldn't know what to do about that. I hope I helped in some way.