This chapter may be changed, altered or amended only by a two- thirds (2/3) vote of the city council. Ordinances proposing changes in limits of use districts, or proposing changes in permissible conforming uses within respective districts, shall not receive final passage until after a public hearing before the city council to be held on notice to be given by the city clerk by publication in the official paper of the city at least fifteen (15) days before the date of hearing, and said notice shall clearly reflect and submit the proposed changes. (1982 Code § 9.321)