Any insurer may apply to the commissioner for permission to effect a uniform percentage increase or decrease in the rates applied to all risks of a particular class in the state in a particular kind, or kinds, of insurance. Upon the filing of such application, the commissioner shall give notice thereof by registered or certified mail to the rating organization, if any, of which such insurer is a member or subscriber and shall fix a time and place for a hearing upon the merits of such application. At such hearing, such insurer and such rating organization, or their representatives, shall be entitled to be heard and to present evidence in support of, or against, such application. The commissioner shall, upon the conclusion of such hearing, make such order as he shall deem consistent with the establishment and maintenance of reasonable, adequate and non-discriminatory rates. If the application is granted, such increase or decrease shall remain in force unless withdrawn by the insurer with the consent of, or by order of, the commissioner. If the commissioner shall find that such increase or decrease will result in rates that are unreasonable, inadequate, or unfairly discriminatory, he shall make an order denying the application. Notwithstanding the foregoing, but subject to the provisions of Section 27-13-30, to the extent not inconsistent therewith, when a filing of adjustments of rates for existing rating systems is made under this section and does not involve a change in the relationship between such rates and the expense portion thereof or does not involve a change of the element of expenses which are paid as a percentage of premiums and does not involve a change in rate relativities among such classifications on any basis other than loss experience, such filing shall become effective upon the date, or dates, specified in the filing and shall be deemed to meet the requirements of this title. A rate in excess of that promulgated by such rating organization may be charged on any specific risk provided such higher rate is charged with the knowledge and written consent of both the insured and the commissioner.