BlackBerry Desktop Manager will only show the OS versions officially released by the carrier to which the device is branded.
If no update is showing, then the device has the latest version released by that carrier.
If you want to update, then you will have to download the OS released by another carrier to your computer, install it on the computer, and then install it to the device.
However, if you are new to BlackBerry devices and updating the OS, then you really should wait and get to know the device and how it works before attempting the update.
Otherwise, go here. http://www.blackberryforums.com/gene...languages.html