To download the entire chat history you have had with a contact, follow the steps given below.
Navigate to SMS Chat.
The SMS Chat page will be displayed.
Select the contact you wish to download its chat history from the SMS chat list on the left side.
The selected contact’s chat details will be displayed on the right side.
3. Select Download Chat History () option from the Actions drop down list.
The chat history of the selected contact will be downloaded to your computer in the CSV format.