(US specific) Provided by an employer-sponsored self-funded ERISA plan. The company generally advertises that they have one of the big insurance companies. However, in an ERISA case, that insurance company "doesn't engage in the act of insurance", they just administer it. Therefore, ERISA plans are not subject to state laws. ERISA plans are governed by federal law under the jurisdiction of the US Department of Labor (USDOL). The specific benefits or coverage details are found in the Summary Plan Description (SPD). An appeal must go through the insurance company, then to the Employer's Plan Fiduciary. If still required, the Fiduciary's decision can be brought to the USDOL to review for ERISA compliance, and then file a lawsuit in federal court.
Some, if not most, health care providers in the United States will agree to bill the insurance company if patients are willing to sign an agreement that they will be responsible for the amount that the insurance company doesn't pay. The insurance company pays out of network providers according to "reasonable and customary" charges, which may be less than the provider's usual fee. The provider may also have a separate contract with the insurer to accept what amounts to a discounted rate or capitation to the provider's standard charges. It generally costs the patient less to use an in-network provider.
Premiums subsidies are still available in the exchange for people with income up to 400 percent of the poverty level. (For 2018 coverage, a single person can earn up to $48,240 and be eligible for the premium tax credit, and a family of four can earn up to $98,400). Calculate your subsidy. In 2017, 84 percent of exchange enrollees received premium subsidies that covered an average of two-thirds of the total premiums.