I have a hunch that if you have a car with OnStar, the best way to go might be pulling the fuse for that or finding some other way of disconnecting it. If it’s an older vehicle & you have no practical use for OnStar (like paying for the subscription) you may as well disconnect it. The company that built it already knows enough about it, except maybe for frequency of breakdowns.
Even if you don’t pay the subscription the OnStar unit is still broadcasting sending location data to it home server.