You can blacklist mobile numbers so that incoming messages from the blacklisted will not be billed from Settings -> Blacklist
Blacklisted Numbers : Here you can type and enter to create blacklist numbers, please ensure the number should be entered with country code without + or 0
Takenover Numbers : Takenover means the numbers which are current takenover by the Live Chat i.e subscribers are currently chatting through Live Chat and Smart replies is disabled for them, you can manually remove those numbers from here
Optout : Optout is only for WhatsApp Shared Number where the user sends the message with the "STOP" followed by the keyword like "#PICKY STOP" and user will automatically added into the Optout list, when the user sends the message again they will be removed from the optout list. You can also manually add the numbers into optout list.