I had OnStar included with my car in 2014, and have had the unfortunate benefit of having to rely on it when someone pulled out in front of me and I T-Boned a young kid in his relative's Mini Van. Airbag went off and completely destroyed by Left Wrist (Yes, I am still able to play guitar after much PT). In my opinion, OnStar saved my life. But BOY is it expensive. Is it worth the high cost, knowing it's just more insurance you pay for and only use, MAYBE, if you need it? Sure. But OnStar also lets me start my Car from my Phone and locate it from anywhere. Being able to start my Car at work far from my car on a super cold day is something I used ALL THE TIME. But ultimately found it to be too pricey. But to answer your Main Question, you just press the built in OnStar button and it connects you with someone who can start all the billing stuff for you. The good thing about OnStar, though, is that if you DO crash, it contacts YOU. If you're unconscious in your car, and they're talking to you and you don't respond, that's just another indicator for them to hurry the F up.
What would Apple have to charge extra for this? Why can't some feature people will want to rely on, but NOT use all the time (like I did with OnStar), just be included in AppleCare+ or even AppleOne+ or whatever... People aren't going to be roaming and texting or calling people for fun. It's going to be something their life will depend on in a desperate life threatening moment. To find out THEN that you'd have to pay extra to have an Ambulance come and get you??