I am looking for a way to automatically send all callers that aren't in my contacts straight to voicemail. Either alli the time, or just when I am at work. I want my contact to be able to call me, but everyone else to voicemail. Is this possible natively in Oreo or is there an app I need? P.s. My cell carrier is US CELLULAR and they do not have a dedicated voicemail app like sprint and T-Mobile.