Device operating system releases are "released" by specific carriers once they have certified and trained their support techs, but still, you are able to load to any carrier's same model by following the instructions below.
See the link below, for the download and simple installation instructions.
Do a backup of your device first, using Desktop Manager > Backup. Close Desktop Manager upon completion.
1. Download the OS file to the PC then install it to the PC by running (double clicking) the file you downloaded.
2. Go to c:\program files\common files\research in motion\apploader and delete the file named "vendor.xml."
3. Plug in BB and double click on "Loader.exe." It's located in the same place as the above vendor.xml file.