Nothing contained in this division shall be construed as inhibiting or precluding the city from adopting a supplemental schedule of rates, charges and rentals to be made applicable to the city's municipal water and sewer system; however, so long as any of the city's "Water and Sewer Refunding and Improvement Revenue Bonds" to be dated February 1, 1967, remain outstanding and unpaid, such rates and charges shall not be reduced except in accordance with the terms of the ordinance to be adopted by the city authorizing the issuance and sale of the bonds.
(Code 1977, § 11.210(8))