OnStar doesn't care. They don't care if you're speeding. They don't care if you're racing. They don't care if you're a drug addict. They don't care if you like to have sex in your car. They don't care. They aren't listening unless the car requests OnStar.
OnStar is a call center. They receive calls from cars. Those calls are only initiated by the car because you either pushed the OnStar button or
your car's crash sensor were activated. There is no other reason for OnStar to be on your phone.
"But I got a call in my car from someone trying to sell me stuff." I know. I'm sorry. I'm sure you've been called on telemarketers on your home or cell phone, too. Am I right?

Do you know how I knew that? All phones
can receive calls. OnStar does include a phone, but it does not mean that
the person on the other end of the phone is necessarily an OnStar representative. That's how you can call your mom from your car by saying "dial" and then your mom's number. Just because you have an AT&T phone doesn't mean you're only using the phone to call AT&T. Other people can call that number.
That is not spying.
OnStar is
not trying to hold down a revolution or anything. None of us are trying to revolt.
And from what would we be revolting? If we didn't want a Chevrolet,
we have the free will to choose something else, so OnStar is not somehow enforcing the will of General Motors on us.
Let's talk about OnStar customer service associates. They are
just like you. They go to work. They do their job. They go home. Do you think they care what happens in your car? If they did care,
what would motivate them? Does your anti-OnStar conspiracy theory consider this?

Would it take commissions and bonuses to make people care about what happens in your car?
How big of a commission would it take for you to care what happens in my car? 
This is what OnStar reps are thinking if they are reading these threads.
They don't care.
Let me tell you
what does matter to OnStar representatives. They want you to
buy OnStar. If you're scared of OnStar and don't buy OnStar, OnStar does not make
money. They can lose their jobs if that happens too much, so they want to provide awesome customer service and sell profit generators that
make you want to buy the service. That's all they want.

Just like you want to be relevant at your job, OnStar reps want to be relevant at their jobs. They want you to want their service so they can keep their jobs.
Let's summarize: OnStar doesn't care what happens in your car.