When turned on, all incoming calls that are not in the Block List will be immediately sent to voicemail. A custom text message option is available that will automatically be sent to the caller, up to 160 characters, to let them know you are currently not available. This feature is intended to be used only when you do not wish to be bothered by phone calls.
How do I block a number by name?
How do I block Restricted, Private, Unknown, or Anonymous calls with Call Detector?