In Arkansas Louisiana Gas Co v. Hall, 453 U.S. 571,577 (1981) the Court relied heavily on the nondiscrimination strand to deny relief. 453 U.S. at 571. There, the plaintiffs, natural gas producers, sued a customer to recover an unfiled gas rate under the parties purchase agreement. Id. at 573-74. The parties agreement contained a favored nations clause, which allowed the plaintiffs to charge the defendant at a rate higher than the filed rate if the defendant ever purchased . . . gas from another party at a rate higher than the one it was paying the plaintiffs. Id. at 573. Relying on the filed rate doctrine, the Court recognized that the considerations underlying the doctrine . . . are preservation of the agencys primary jurisdiction over reasonableness of rates and the need to insure that regulated companies charge only those rates of which the agency has been made cognizant. Id. at 577-78. In Arkansas Louisiana Gas Co. v. Hall, 453 U.S. 571, 101 S.Ct. 2925, 69 L.Ed.2d 856 (1981) ("Arkla "), the Supreme Court held that a seller (or buyer) may not sue to change a filed rate even if the buyer (or seller) has contracted to change that rate. Hall sold gas to Arkla from the Sligo Field for a fixed price, but Arkla promised to pay Hall as high a price as it paid to any other producer for Sligo Field gas. Arkla then bought Sligo Field gas from the United States for a higher price than it paid to Hall. Hall discovered Arkla's breach and sued to recover the difference between the price paid to him and the price Arkla paid to the United States. The Supreme Court rejected Hall's suit and reiterated the filed rate doctrine announced in Montana-Dakota: regulated sellers must charge only the rate filed with the FERC, and only the FERC--not a court--may change an unreasonable filed rate. 453 U.S. at 577-78, 101 S.Ct. at 2930-31. Moreover, even the FERC may not alter a rate retroactively or order reparations for unreasonable charges in the past. Id. Hall wanted simply a retroactive rate increase, so his claim, based on state contract law, was preempted. Id. at 579, 584, 101 S.Ct. at 2931, 2934.