How do I connect/disconnect from the Underground free WiFi?

1. Open your Wi-Fi settings while you’re in a station.
2. Choose the network called Three_WiFi.
3. If your phone asks how to sign in, choose AKA from the list, then Connect. Your phone signs in using your SIM, so there’s no password.

To stop using it, turn Wi-Fi off, or tap the network and choose Forget.