No change shall be made in any rate, fare, charge or classification, or any rule, regulation or practice affecting such rate, fare, charge or classification, or the value of the service thereunder, specified in any effective tariff or schedule of rates of a transportation company, except after 30 days’ notice of the proposed change, filed and posted in accordance with Section 37-2-10 and the rules and regulations of the commission adopted thereunder. Such notice shall plainly state the change proposed to be made and the time when such change will take effect. The commission may, in its discretion and for good cause shown, allow such change upon notice less than that herein specified.