A company shall not directly or indirectly or by any special rate, rebate, drawback, or other device or method make any deviation from the rates, fares, charges, or prices for any service rendered by it or in services rendered or to be rendered in connection with services, as specified in its schedules of charges in effect at the time the service was rendered. No company may enter into any contract, agreement, or arrangement relating to the furnishing or rendering of any special product or special service not provided for or covered in the schedule without prior filing with the Agency. However, nothing in this section shall prohibit the giving by any company of free or reduced rate service to its employees, or in case of public emergency, or to the classes defined and provided for in the Act of Congress entitled "An Act to Regulate Commerce" and amendments to that Act. (Added 1985, No. 224 (Adj. Sess.), § 1.)