The designated agency shall supervise in the manner provided by this subchapter each hospital operating under a certificate of public advantage issued under this chapter to ensure that the immunized conduct of a merged entity furthers the purposes of this chapter. A change in rates for hospital services operating under a certificate of public advantage issued under this chapter may not take effect without prior approval of the designated agency as provided by this section. See definition section Tex. Health & Safety Code § 314A.001.