Wash. Rev. Code § 80.36.140
Whenever the commission shall find, after a hearing had upon its own motion or upon complaint, that the rates, charges, tolls or rentals demanded, exacted, charged or collected by any telecommunications company for the transmission of messages by telecommunications, or for the rental or use of any telecommunications line, instrument, wire, appliance, apparatus or device or any telecommunications receiver, transmitter, instrument, wire, cable, apparatus, conduit, machine, appliance or device, or any telecommunications extension or extension system, or that the rules, regulations or practices of any telecommunications company affecting such rates, charges, tolls, rentals or service are unjust, unreasonable, unjustly discriminatory or unduly preferential, or in anywise in violation of law, or that such rates, charges, tolls or rentals are insufficient to yield reasonable compensation for the service rendered, the commission shall determine the just and reasonable rates, charges, tolls or rentals to be thereafter observed and in force, and fix the same by order as provided in this title.
Whenever the commission shall find, after such hearing that the rules, regulations or practices of any telecommunications company are unjust or unreasonable, or that the equipment, facilities or service of any telecommunications company is inadequate, inefficient, improper or insufficient, the commission shall determine the just, reasonable, proper, adequate and efficient rules, regulations, practices, equipment, facilities and service to be thereafter installed, observed and used, and fix the same by order or rule as provided in this title.
RCW 80.36.140