SunStar EMS transport bill and additional insurance

I went to the hospital recently and the transport company SunStar EMS is trying to bill me not you my insurance company at the same time they are trying to sell me additional insurance. At this point in time, they are threating to take it to collections what action should I take. I am covered or this was my understanding please inform me if I am mistaken and require additional insurance on top of what the company provides so I can bring it up at the next company meeting.