By default, BB10 has option to block all incoming calls or none. Not individually. If we block individual call, I hear a ring once and then it goes to busy. Instead, we can just ignore. Disable all notifications for a number if we want to ignore the call. For that, first save the annoying number to your contacts and in the Ringtones and Notifications option for that contact, choose Phone Calls and turn off All Notifications. Now the call gets received, but you would not know unless you check the phone. No disturbances.