This is an original petition for a writ of certiorari filed by the Manila Electric Company against the Public Service Commission and Moises Ampil praying for the  issuance, after the necessary proceedings, of an order declaring said commission's resolution of September 13, 1935, in case No. 42170 thereof, null and void, for lack of jurisdiction  to render it.

The pertinent facts necessary for  the resolution of the legal  question raised in the present petition, which are inferred from the petition and the documents attached thereto, are as follows:

The respondent Moises  Ampil is an operator of an auto-calesa service in the  City of Manila  and neighboring municipalities, with a certificate of public convenience duly issued by the respondent  Public Service Commission.  On December 29,1934, the petitioner Manila Electric Company filed a complaint with said commission against the respondent Moises Ampil for charging passenger rates less than what  he was  authorized  to charge, which complaint was registered as case No. 42170.   In the decision rendered by said commission on August 9,  1935, in said complaint and in three others later  filed against said respondent Moises Ampil,  it was ordered that  his certificate of public  convenience be suspended for a period of six months (Exhibit  A).

On August 25, 1935, the Public Service Commission rendered  another joint  decision  in  three other complaints against said respondent Moises Ampil, which were registered as Nos. 42726, 42820 and 42907, ordering him to pay the nominal costs of investigation at the rate of P25 for each case (Exhibit B).

On August 28, 1935, the petitioner Manila Electric Company filed a petition for a rehearing  in the above  cited case No.  42820, protesting  against the imposition simply of nominal costs of investigation upon the respondent Moises Ampil (Exhibit B-1).

On September 3, 1935, the  Public Service Commission denied said  motion for a rehearing on  the ground that the certificate of public convenience of the respondent Moises Ampil was  then  under  suspension for six months.

On September 11, 1935,  the respondent Moises Ampil filed a motion in said case No. 42170, praying that the suspension of  his  certificate  of public convenience for six months be lifted (Exhibit C).

On September 13, 1935, the petitioner Manila Electric Company  filed a motion praying for the denial of said motion of the respondent Moises Ampil, dated September 11, 1935  (Exhibit  C-1).   On the same date, September 13, 1935, the  respondent Public Service Commission, without hearing the parties or serving notice to the petitioner, granted the motion of  the  respondent Moises Ampil,  of September 11, 1935 (Exhibit D).

On September  16, 1935, the petitioner Manila Electric Company  was served with a copy of the resolution of September 13, 1935, rendered in case No. 42170.  On the same date, September 16, 1935, the petitioner filed a motion for a rehearing (Exhibit E), which was  set for hearing on September 23, 1935. On said date the respondent Moises Ampil appeared through his attorney, waived his right to present evidence  in support of his motion of September 11,  1935 (Exhibit  C), and asked for  permission  to  file a memorandum which was granted.

On September 30, 1935, the Public Service Commission denied  the petitioner's  motion for a  rehearing of September 16, 1935 (Exhibit F).

The only question to be decided in this case is whether or not  the Public Service Commission has jurisdiction to cancel the suspension of a certificate  of public convenience ordered by it before the lapse of the period of suspension fixed in the order.

Section 28 of Act No. 3108 provides as follows:

"Sec.  28. The Commission,  at  any time, may order a rehearing to  extend, revoke, or modify  any order made by it.   Once a case has been decided after the  rehearing, any  interested party may, if he so desires, take an appeal to the Supreme Court by following the procedure prescribed in section thirty-five of  this Act, and  in this case the Com- mission may stay the effects of the order made by it during the pendency  of such appeal."

Under the legal provision above quoted, the Public Service Commission,  at  any time,  may order a rehearing to modify  any order made  by  it.  The order of  December 29, 1934, issued in case No. 42170, directing the suspension of the respondent Moises Ampil's certificate of public convenience for a period of six  months  is among those that, at any time after a rehearing, may be modified under section 28 above quoted.

The  petitioner contends that, said  order of suspension having become final, the commission could no longer amend it, citing in support of  his theory the doctrine laid  down in the case of Manila Electric Company vs.  Public Service Commission (61 Phil., 456).  In said  case this court said:

"Once questions are decided by the  Public Service Commission and confirmed by the Supreme Court, neither  the Public  Service Commission nor the  Supreme  Court can be expected to go over and over again the same questions. Nor should the Public Service Commission attempt to review a decision of the  Supreme Court.  Finality must be written on Public Service Commission  cases just as public policy demands that it be  written on  judicial controversies."

The  above quoted  doctrine does not  prevent the commission,  for  just cause,  and when the circumstances of each case and public policy so  require, from  extending, revoking or modifying an order made by it after said order has become final.  What this court meant is that once a question  has been definitely  decided and the  decision has become final, that same question cannot again  be raised between the same parties.  The orders of the Public Service  Commission are  subject  to changes  and  alterations whenever public  policy and  the needs  of  public services so require, always after a rehearing in accordance with section 28 of Act No.  3108, as amended.  The order of suspension of a certificate of public convenience issued by the Public Service Commission is of the nature of a disciplinary measure affecting only the service whose certificate of public convenience has been  suspended, and, as such, the commission  has ample powers to cancel it either on petition of the parties or motu proprio, when in its opinion it is justified by the  circumstances of the case  and public policy so demands.

As to the question  raised by the petitioner Manila Electric Company that there was no rehearing  before the cancellation of the order  of suspension of the certificate of public convenience issued in favor of the respondent Moises Ampil in case No. 42170 was granted, while it is true that no such  rehearing was had  and the Public Service Commission therein acted in violation of section 28  of Act No. 3108, as amended, the rehearing granted by virtue of said petitioner's  motion of  September 16, 1935 (Exhibit E), which rehearing was held on September 23,1935, cured said omission.

For the foregoing considerations, we are of the opinion and so hold that the  Public Service Commission, after a rehearing, has discretionary power to cancel an  order of suspension of  a certificate of public convenience when it is justified by the circumstances of the case and public policy so demands.

Wherefore,  not finding any merit in the petition  for certiorari before us, it is denied and dismissed, with costs to the petitioner.  So ordered.

Avanceña, C. J.,  Abad Santos, Diaz, Recto, and Laurel, JJ., concur.