When the phone is at the operator screen (the normal standby screen) press *#0000# to check the version
If its only 10.0.0.xx or 11.0.0.28 then you may be able to update to the latest version, which is 12.0.0.xx
Download the Nokia Updater:
Nokia Europe - Phone software update
Install NSU and connect your phone to the PC using USB, connect using PC Suite Mode.
The NSU software will check for an update and download the ~100MB firmware file. If your phone is branded, you may not be able to update the firmware as yet. Your provider needs to approve the new firmware, then Nokia will make it available via NSU (Nokia Software Updater).