Every public utility shall file with the commission copies of contracts, agreements or arrangements to which it may be a party, as the commission may designate. Every public utility shall, whenever required by the commission, file with the commission statements of passes, tickets, mileage books or franks, issued by the public utility, free or at rates lower than those open to the public in general, or of other authorization of service free or at reduced rates, these statements to cover the periods of time and classes of service, and to include information connected with the issuance thereof, as the commission may prescribe.
W.S. 37-3-111