It shall be unlawful for any person except a medical service corporation incorporated in accordance with this chapter and operating in accordance with authority from the Commissioner to establish, maintain, or operate a medical service plan or to solicit subscribers to or enter into contracts with respect to a medical service plan, provided that the medical service corporations with the approval of the Commissioner may enter into an agency contract with any licensed nonprofit hospital service corporation; provided, further, that nothing in this chapter shall be construed as preventing a person from furnishing medical services for the prevention of disease among his employees or from furnishing such medical services as are required under the workers' compensation or other laws of this state or as preventing any duly licensed insurance company from writing medical indemnity insurance.