Whenever the Commission after a hearing, upon its own motion or upon complaint, finds that the existing rates in effect and collected by any radio common carrier for any service are unjust, unreasonable, insufficient or unreasonably discriminatory, or in any way in violation of any provision of law, the Commission shall determine the just, reasonable, and sufficient rates to be thereafter observed and in force, and shall fix such rates by its order. In determining just, reasonable and sufficient rates the Commission shall give due consideration to the radio common carrier's property devoted to the public service; the revenues received for the service; the reasonable operating expenses and other costs necessary to provide the service; the total earnings required for the proper discharge of the radio common carrier's public duty; the capitalization of the radio common carrier and the net income required on its net worth; and such other matters, circumstances and conditions as the Commission may find necessary. Provided, that the rates so fixed shall not be higher than necessary to give a fair return to the stockholders.