Ala. Code § 37-1-86

(a) Before proceeding to make such investigation, the commission shall give the utility and the complainant at least 10 days’ notice of the time and place when and where such matters will be considered and determined, and all parties shall be entitled to be heard, through themselves or their counsel, and shall have process to enforce the attendance of witnesses.

(b) Whenever the commission shall make any order or determination, or issue any subpoena, notice or writ, notice thereof may be served on the person affected thereby by delivering a copy of such order, subpoena, notice or writ, signed by or in the name of the chairman of the commission, to any such person or an officer or agent of such person, if a corporation, as in the case of civil process, which service may be executed by any member of the commission, the secretary or any employee thereof, or by any sheriff of the state, and a copy of such order, subpoena, notice or writ, with the service endorsed thereon, must be returned to the commission and entered of record as a part of the proceedings, and such endorsement and return shall be prima facie evidence that such order, subpoena, notice or writ has been duly served.