O2 customers can now get access to the carrier's faster 4G network on their iPhone 5s or iPhone 5c thanks to a quick update. Here's how to activate O2 4G on iPhone 5s, iPhone 5c. If you've got a new iPhone with a pay monthly 4G-ready SIM, you'll need to connect your iPhone to iTunes or WiFi. If you've connected to iTunes, you should then see a Window that asks you to install carrier update settings. Click 'Update settings' now, which will begin the update and before you know it, you'll be able to connect to speedy 4G internet. If you connected via WiFi, you can go to Settings > General
