Backup iPhone SMS to your system

Using Backup With iTunes, make sure you select back up to “This Computer” option and not with iCloud. Then press the ‘Back up Now’ button. When the backup is done search for the SMS data file and you can make a copy of it and keep it. The SMS backup file named ‘3d0d7e5fb2ce288813306e4d4636395e047a3d28’ is located in different paths depending on the OS you are using.
Mac OS
User- > Library -> Application Support -> MobileSync -> Backup.
In Windows XP
Documents and Settings -> username -> Application Data -> Apple Computer -> MobileSync -> Backup.
Windows 7 /8
Users -> yusername -> AppData -> Roaming -> Apple Computer -> MobileSync- > Backup.
Inside the Backup folder, there is another folder named randomly with numbers and letters. Select the folder that is most recently modified.