Any contract that has been approved as provided in ORS 758.400 to 758.475 may be subsequently amended by the parties thereto, but any such amendatory agreement shall be filed with the Public Utility Commission and shall thereafter be approved or disapproved by the commission in the manner provided in ORS 758.420 and 758.425. However, no hearing is required if all affected customers approve the amendatory agreement. An amendatory agreement may be enforced in the manner provided in ORS 758.465.
ORS 758.430