Whenever there is filed with the Commission any new or revised charge, classification, regulation, or practice, the Commission may either upon complaint or upon its own initiative without complaint, upon reasonable notice, enter upon a hearing concerning the lawfulness thereof; and pending such hearing and the decision thereon the Commission, upon delivering to the carrier or carriers affected thereby a statement in writing of its reasons for such suspension, may suspend the operation of such charge, classification, regulation, or practice, in whole or in part but not for a longer period than five months beyond the time when it would otherwise go into effect; and after full hearing the Commission may make such order with reference thereto as would be proper in a proceeding initiated after such charge, classification, regulation, or practice had become effective. If the proceeding has not been concluded and an order made within the period of the suspension, the proposed new or revised charge, classification, regulation, or practice shall go into effect at the end of such period; but in case of a p

roposed charge for a new service or a revised charge, the Commission may by order require the interested carrier or carriers to keep accurate account of all amounts received by reason of such charge for a new service or revised charge, specifying by whom and in whose behalf such amounts are paid, and upon completion of the hearing and decision may by further order require the interested carrier or carriers to refund, with interest, to the persons in whose behalf such amounts were paid, such portion of such charge for a new service or revised charges as by its decision shall be found not justified. At any hearing involving a new or revised charge, or a proposed new or revised charge, the burden of proof to show that the new or revised charge, or proposed charge, is just and reasonable shall be upon the carrier, and the Commission shall give to the hearing and decision of such questions preference over all other questions pending before it and decide the same as speedily as possible.

A local exchange carrier may file with the Commission a new or revised charge, classification, regulation, or practice on a streamlined basis. Any such charge, classification, regulation, or practice shall be deemed lawful and shall be effective 7 days (in the case of a reduction in rates) or 15 days (in the case of an increase in rates) after the date on which it is filed with the Commission unless the Commission takes action under paragraph (1) before the end of that 7-day or 15-day period, as is appropriate.