No change shall be made in any schedule, including schedules of joint rates, except upon 10 days notice to the Commission, and all such changes shall be plainly indicated upon existing schedules, or by filing new schedules in lieu thereof 10 days prior to the time the same are to take effect; provided, that the Commission, upon application of any public utility, may prescribe a less time within which a reduction may be made.
D.C. Code § 34-1127
Rate change procedures, appeal and review, see § 34-901. Rate changes, approval of Commission, see § 34-601. .