OnStar reports location and speed data to the car manufacturer. Sometimes they will sell this data to insurance companies to raise your premium, as several news stores pointed out a few weeks ago. I couldn't really find an advantage to OnStar, (I have my phone to call emergency services) so I disabled it by pulling it's fuse.
For my 2019 bolt, it's f31 in the instrument panel fuse box, just down and to the left of the steering wheel. The fuse box cover comes off when you pull it hard from the bottom.
I was able to find which fuse went to OnStar in the owners manual and labeled on the inside of the fuse box cover. You should be able to find it for your model car there too if it uses OnStar.
I did have the casualty of my speaker for calls and texts. I'm not able to use it right now. I'll see if I can dig in and reconnect it somehow, but we'll see.
Who knows that other into they're snitching back to GM, or what they could do in the future, so I recommend disconnecting it. Good luck!
You can promote and share articles such as the Mozilla research that this outrage came from to raise awareness and a coalition of like-minded, privacy-focused individuals.
You can donate to non profits that are dedicated to bringing these privacy invasions to light and fighting them such as the EFF or the Mozilla Foundation.
You can write to your Senators or your Representative to let them know you’re unhappy with how these companies are treating your legislators’ constituents.
I have done all of the three above and I can at least say that I’m doing my part even if I’m not going to the GM R&D facility.