No change shall be made in the charges, classifications, regulations, or practices which have been so filed and published except after one hundred and twenty days notice to the Commission and to the public, which shall be published in such form and contain such information as the Commission may by regulations prescribe.

The Commission may, in its discretion and for good cause shown, modify any requirement made by or under the authority of this section either in particular instances or by general order applicable to special circumstances or conditions except that the Commission may not require the notice period specified in paragraph (1) to be more than one hundred and twenty days.