Hope you're correct. What's the source of your information? And how is the connection being made??
The I-Pace, as well as most cars these days, have 2 SIMS, one 'built-in', in JLR land it is referred to as the 'Telematics SIM' and one controlled by the user, the 'Personal SIM'. Your JLR retailer should be able to explain it to you, as it is not unique to the I-Pace and has been that way for several years.
Every new car I have purchased in at least the last 5 years has been the same. You do not need to pay ATT to use the basic functions of the car. For extended functions, such as using the car as a hotspot or to get live traffic updates, etc., you will need a 'commercial' internet connection, whether that is using the 'Personal SIM' in the car along with a purchased data plan or by connecting your car to the internet using your phone as a hotspot. Some manufacturers (BMW/Porsche) are starting to bundle extended functions into internal subscription programs (like OnStar has been for years) and I would expect that will be the way of the future as they realize it is another relatively easy revenue stream for them, rather than turfing off a data rate plan to a 3rd party vendor. I expect in the future the free functions will be reduced to basic emergency services and vehicle updates and no manufacturer will provide anything outside that for free.
Currently this is what paying ATT will do for you, nothing more:
From the ATT website:
"What are the benefits of subscribing to data service for my vehicle?
Access your vehicle's built-in hotspot
Connect up to 8 Wi-Fi compatible devices
Use your favorite apps, visit your favorite sites
Get a reliable connection with your vehicle's antenna
Use your vehicle's built-in hotspot instead of your smartphone to connect devices and use less of your smartphone's battery!
Plus, if you keep your vehicle hotspot set to 'on' it conveniently allows compatible devices to re-connect automatically and use the vehicle's hotspot data unless the vehicle is removed as a hotspot from the returning device's settings."
If you look at your Jaguar InControl account, you will see it is a 5 year subscription plan included with the car. I'm not sure what happens after 5 years...I've never kept a car more than 3.