I'm running the latest iOS 6.0.1 on an iPhone 4, and this is a problem that existed since iOS 6. The problem occurs when you set the Do Not Disturb function to allow only calls from your contacts (or a certain group in your address book). When you remove any contacts from the address book, the logical result will be that the removed contact's number will be silenced with Do Not Disturb turned on. But that's not the case. Calls from contacts that have been removed, still comes through and is not silenced. I'm lead to believe that the Do Not Disturb uses a different database than the address book. I've tried disabling Do Not Disturb and turning it back on again as well as resetting and restoring the iPhone, but neither worked. This is a very annoying bug, and I would've posted on the apple support community but I come across "An unknown error has occurred." when I tried to log in the apple support site. Sigh. Someone with an other suggestion?