Doesn't matter, it's all of them. My family has had United Healthcare, Cigna, and Anthem in the past 6 years and they're all equally bad. We've had so many issues with coverage for both of my autistic children and mental health care.
The system is designed to screw you unless you have hours of time to question every bill. Luckily my wife doesn't have a job so she can make all of these calls. In most cases we got everything resolved, but after my wife basically made this her daytime job calling about the bills and learning about how billing and coding works.
After our experience, I'm confident that no one knows what they are doing. It's all guesswork. From the doctors, to their office billing people, to the insurance. It's all fucked.
Yup, we always hit our deductible within about 2-3 months due to my kid's therapy, yet we still get full bills from all of our providers even though we should be 90-100% covered at that point. You call the insurance, they say the provider billed it wrong, you call the provider's office and they refuse that they did anything wrong and tell you to call your insurance. It's a never ending cycle.