This is how to install the Hi application on your iPhone to allow you to register your card and track your balance.
Open the App Store on your Apple Phone
When the app store opens, go to the bottom right and select the search option.
Search for hi. group, and you will have the option to install if you have not done so already or the option to open it if it's been installed
once the app is installed, you can find it in the search function on your phone
Press and hold the icon to add it to your home screen or access it through your app tray.
You can now log on to the application and view your details/card.
This article explains How To Sign-in To The App.