Tex. Util. Code § 104.151
(a) If the regulatory authority, on its own motion or on complaint by an affected person, after reasonable notice and hearing, finds that the existing rates of a gas utility for a service are unreasonable or in violation of law, the regulatory authority shall:
Acts 1997, 75th Leg., ch. 166, Sec. 1, eff. Sept. 1, 1997.