The best way to chat without showing online and not change your last is to use an instant messaging app with offline mode, such as WhatsApp or Viber. These apps allow you to send messages without appearing online and without changing your last seen status. Other websites, such as Facebook Messenger, have privacy settings that allow you to chat without showing online. Another option is to use a web-based chat service that allows you to go offline and remain invisible while still being able to chat.