Wash. Rev. Code § 80.36.190
No telecommunications company subject to the provisions of this title shall charge or receive any greater compensation in the aggregate for the transmission of any long distance conversation or message of like kind for a shorter than for a longer distance over the same line, in the same direction, within this state, the shorter being included within the longer distance, or charge any greater compensation for a through service than the aggregate of the intermediate rates subject to the provision of this title, but this shall not be construed as authorizing any such telecommunications company to charge and receive as great a compensation for a shorter as for a longer distance. Upon application of any telecommunications company the commission may, by order, authorize it to charge less for longer than for a shorter distance service for the transmission of conversation or messages in special cases after investigation, but the order must specify and prescribe the extent to which the telecommunications company making such application is relieved from the operation of this section, and only to the extent so specified and prescribed shall any telecommunications company be relieved from the requirements of this section.
RCW 80.36.190