It shall be unlawful for any public utility subject to the provisions of this chapter to make or give any undue or unreasonable preference or advantage to any particular person, company, firm, corporation or locality, or any particular character of traffic or service, in any respect whatsoever, or to subject any particular person, firm, corporation, company or locality, or any particular character of traffic or service, to any undue or unreasonable prejudice or disadvantage in any respect whatsoever.
Nothing in this section shall be construed to prevent the commission from authorizing or requiring any rate design consistent with the purposes and policies set forth in article two-a of this chapter.