The second screen lets the end-user select a new end time.
The Start time will be the previous end time if it’s an extension or the current time if it’s a new purchase.
Tariff calculation is done when the end-user presses any of the buttons or enters a value. All buttons are disabled while waiting for an answer from the server. A message is presented if the end-user enters an invalid value such as a negative time.
The “Buy more time” button will only be enabled if the information is valid.
