O.C.G.A. § 36-38-21

Where there are outstanding bonds and coupons of any municipal corporation of this state, whether such bonds or coupons are due or to become due, the authorities may issue new bonds with coupons attached, to be exchanged and to stand in the place of such outstanding bonds and coupons, provided that the new bonds so issued shall not exceed in amount the previously existing total bonded debt, with interest thereon, of such municipal corporation.