iPhone OS 3.1.2 is available as a free update via iTunes. To install the update, do this:
- Launch iTunes.
- Connect your iPhone to your computer.
- Select your iPhone in the iTunes Library list.
- Click the Summary tab.
- Click Check for Update.
- Click Download and Install.
Some iPhone owners have been reporting that after installing the OS update, they are receiving a carrier settings update as well. So far there isn’t any information available about what the carrier update includes.
iPhone OS 3.1.2 is available for the original iPhone, iPhone 3G and iPhone 3GS.