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!
I'd also like to know!
Looks like pulling the fuse does disable Bluetooth. My phone is still saying it's connected for calls, and it pops up a notification as connected on the screen, but it won't play audio.