Section 29
SEC. 29. Every order made by the Commission shall be served upon the person or public utility, as herein defined, affected thereby, within ten days from the time said order is filed, by personal delivery or by mailing a certified copy thereof to any one of the principal officers or agents of the public utility at his usual place of business, and, in case such certified copy is sent by registered mail, the registry mail receipt shall be prima facie, evidence of the receipt of such order by the public utility in due course of mail. All orders of the Commission to continue service or rates in effect at the time said order is made shall be immediately operative; all other orders shall become effective upon the date specified therein.