Okla. Const. art. XVIII, § 5(a)

Grant, extension or renewal - Approval by voters - Term. No municipal corporation shall ever grant, extend, or renew a franchise, without the approval of a majority of the qualified electors residing within its corporate limits, who shall vote thereon at a general or special election; and the legislative body of any such corporation may submit any such matter for approval or disapproval to such electors at any general municipal election, or call a special election for such purpose at any time upon thirty days' notice; and no franchise shall be granted, extended, or renewed for a longer term than twenty-five years.