Section 99 - Changes in fares and charges; notice required; power of suspension by the commissioner1. Unless the commissioner otherwise orders, no change shall be made in any rate, fare or charge, or joint rate, fare or charge, which shall have been filed and published by a common carrier in compliance with this chapter, except after thirty days' notice to the commissioner and publication for thirty days as required by section ninety-eight, which shall plainly state the changes proposed to be made in the schedule then in force, and the time when the changed rate, fare or charge will go into effect; and all proposed changes shall be shown by printing, filing and publishing new schedules or shall be plainly indicated upon the schedules in force at the time and kept open to public inspection. The commissioner, for good cause shown, may allow changes in rates without requiring the thirty days' notice and publication herein provided for, by duly filing and publishing in such manner as he may direct an order specifying the change so made and the time when it shall take effect; all such changes shall be immediately indicated upon its schedules by the common carrier. Whenever there shall be filed with the commissioner by any common carrier any schedule stating a new individual or joint rate, fare or charge, or any new individual or joint classification or any new individual or joint regulation or practice affecting any rate, fare or charge, the commissioner shall have and he is hereby given authority, either upon complaint or upon his own initiative without complaint, at once, and if he so orders without answer or other formal pleading by the interested carrier or carriers, but upon reasonable notice, to enter upon a hearing concerning the propriety of such rate, charge, fare, classification, regulation or practice; and pending such hearing and decision thereon, the commissioner upon filing with such schedule, and delivering to the carrier or carriers affected thereby, a statement in writing of his reasons for such suspension, may suspend the operation of such schedule and defer the use of such rate, fare, charge, classification, regulation or practice, but not for a longer period than one hundred and twenty days beyond the time when such rate, fare, charge, classification, regulation or practice would otherwise go into effect; and after full hearing whether completed before or after the rate, fare, charge, classification, regulation or practice goes into effect, the commissioner may make such order in reference to such rate, fare, charge, classification, regulation or practice, as would be proper in a proceeding initiated after the rate, fare, charge, classification, regulation or practice had become effective. Provided, that if any such hearing cannot be concluded within the period of suspension, as above stated, the commissioner may, in his discretion, extend the time of suspension for a further period not exceeding six months. The commissioner may as authorized by subdivision one of section one hundred nineteen establish temporary rates for any period of suspension under this section. At any hearing involving a rate, the burden of proof to show that the change in rate if proposed by the common carrier, or that the existing rate, if on motion of the commissioner or in a complaint filed with the commissioner it is proposed to reduce the rate, is just and reasonable shall be upon the common carrier; and the commissioner may give to the hearing and decision of such questions preference over all other questions pending before him and decide the same as speedily as possible.