I have been receiving spam calls and text messages from unknown numbers. I would like notifications for calls and text messages from unknown numbers to be silent. I can't find a way to set up this type of filter. From what I understand about Do Not Disturb mode, it will silence all notification sounds except calls from known contacts. I do not want to silence alerts for messages from known contacts, or my app notification sounds (such as Mail). I noticed I can set custom ringtones and alert sounds for my contacts, but there is no option to set the default global ringtone to "None". Also, there is no mode to edit multiple contacts simultaneously, so the task is very time consuming. I use a contact list synced via Gmail. One suggestion I've read about is creating a Spam contact, blocking it, and adding unwanted numbers to it, but this still allows first time calls through. I do not care if I miss a sincere call from someone if they are not in my contacts. I have not jailbreaked.