K.S.A. 40-2,117

Whenever a professional provider provides services or otherwise renders care to a subscriber of a service corporation under arrangements which such professional provider has established with a contracting facility, and the subscriber does not have a choice of obtaining those services from a contracting professional provider, the professional provider rendering those services shall accept the service corporation's allowable charge level as full payment and may bill the subscriber only for deductibles, coinsurance, shared payments and noncovered services as stipulated in the contract between the subscriber and the service corporation.