Wash. Rev. Code § 80.36.338
Each company withdrawing a filed price list shall provide each customer receiving service under the price list with information about the rates, terms, and conditions under which the service will continue to be provided. If the rates, terms, and conditions do not change upon withdrawal of the price list, such rates, terms, and conditions shall be binding to the same extent as the price list. If any of the rates, terms, and conditions do change upon withdrawal of the price list, the company must provide each customer with a reasonable opportunity to decide whether to accept the changed rate, term, or condition. If a customer does not cancel service within thirty days after notice of the change is given, the customer will be deemed to have accepted all the rates, terms, and conditions offered by the company.
RCW 80.36.338