Wash. Rev. Code § 80.36.180
No telecommunications company shall, directly or indirectly, or by any special rate, rebate, drawback or other device or method, unduly or unreasonably charge, demand, collect or receive from any person or corporation a greater or less compensation for any service rendered or to be rendered with respect to communication by telecommunications or in connection therewith, except as authorized in this title or Title 81 RCW than it charges, demands, collects or receives from any other person or corporation for doing a like and contemporaneous service with respect to communication by telecommunications under the same or substantially the same circumstances and conditions. The commission shall have primary jurisdiction to determine whether any rate, regulation, or practice of a telecommunications company violates this section. This section shall not apply to contracts offered by a telecommunications company classified as competitive or to contracts for services classified as competitive under RCW 80.36.320 or 80.36.330.
RCW 80.36.180