Everyone should connect and show signal as long as the radio is turned on if you try to connect to something and you're not on Wi-Fi connection the iPad will tell you that there is not an active data plan. Just like a cell phone as long as there is a Sim card installed it should show a signal. Does not mean it is active or will work
You have signal but no plan to use it. The signal allows you to buy the data plan anytime you have coverage without needing to find a wifi or other computer.