I use Hangouts to chat with friends. As I don't want to keep history, I set it to be turned off. So whenever I chat, in the input line I see a constant message of "History is turned off".
However, when I open Hangouts again, I can see messages that were sent days ago.
A simple question: how can I see older messages with history disabled?
The history setting only affects messages as they are sent. Turning history off doesn't delete old messages that were sent while history was turned on. If you want to delete your old messages as well as stopping new messages being saved, you can do this with Delete in the chat's menu (or Delete history in the web-based client).
Go to settings, apps and touch the app, and click clear data. Now check if you are able to change the settings and the the settings works.
Open the person hangout. You can uncheck conversation history and you can delete conversation.
