I have a 2018 Chevy. I get emails from the dealership that tells me when a light goes off on my dashboard. OnStar will give me monthly reports about my driving tendencies (average speed, aggressive acceleration, etc.).
So now that I know big brother has access to my car, am I able to disconnect it from the grid?
They can most likely control everything in your car remotely. I think your only recourse is to find where the wireless receiver is and try to block/shield it somehow.
see my comment above to u/Bigtortoise
The antenna cover is effectively a Faraday wrap, and it prevents outside signal from being used to communicate or control your vehicle. You may have to look at vehicle specs if you suspect there is more than one antenna.