If the department after a hearing upon its own motion, or upon complaint finds that the rates demanded, observed, charged, or collected by a household goods warehouse operator for or in connection with any service or storage of goods, wares, or merchandise are unjust, unreasonable, discriminatory, preferential, or otherwise illegal, the department shall determine the just and reasonable rates to be thereafter effective and in force for that household goods warehouse operator and fix the rates by an order, which shall determine when the rates go into effect. Before an order is issued under this section, the household goods warehouse operator shall have an opportunity to be heard upon reasonable notice to be determined by the department.