PRL is the Preferred Roaming List. It is a file that lists all of the carriers and towers that your phone is allowed to roam on. The version number is just the number that is tagged to the specific PRL version. As new PRL's become available, the version number will change, just like for updated software. With most new phones, the PRL updates *should* be pushed to the phone automatically, but sometimes they don't. On CDMA carriers, you dial *228 and call it, and you get your specific carrier's welcome message, and select the given option to update your roaming list. It may be different for GSM carriers, your best bet wold be to call CS and ask them how to get an updated PRL (if there is one).
Want a Bluetooth? Eat a BlackBerry.