Windows (32 Bit) Users
- Open a Command Prompt
- Copy and paste the first line below on to the Command Prompt and press enter
- Copy and paste the second line below on to the Command Prompt and press enter
cd "C:\Program Files\iTunes"
iTunes.exe /setPrefInt carrier-testing 1
Windows (64 Bit) Users
- Open a Command Prompt
- Copy and paste the first line below on to the Command Prompt and press enter
- Copy and paste the second line below on to the Command Prompt and press enter
cd "C:\Program Files (x86)\iTunes"
iTunes.exe /setPrefInt carrier-testing 1
Install TFW 15.6
- Launch iTunes
- Hold the Option (ALT) (Mac)
- Hold the Shift key (Windows)
- Click the Check for Update button
- Select and install ATT_TFW_US_iPhone.ipcc
After I installed TFW 15.6, I needed to go to Settings->General->Reset->Reset All Settingsbefore the 3G indicator would change back to 4G.