Note: Unfortunately there is no chat history backup system on Nokia S40 phones, so there is no way to recover lost chat history data.
In order to export your chat history you need to have a memory card.
In addition, the phone number used for backing up and restoring must be the same.
You cannot restore the chat history from another Whats App account.
The term chat room, or chatroom, is primarily used to describe any form of synchronous conferencing, occasionally even asynchronous conferencing.