The commission, or any person, corporation, or municipal corporation having an interest in the subject matter, or any public utility concerned, may complain in writing, setting forth any act or thing done or omitted to be done by any public utility in violation, or claimed violation, of any law which the commission has jurisdiction to administer, or of any regulation or order of the commission. Any public utility, or other person, or corporation likewise may complain of any regulation or order of the commission, which the complainant is or has been required by the commission to observe or carry into effect. The Commonwealth through the Attorney General may be a complainant before the commission in any matter solely as an advocate for the Commonwealth as a consumer of public utility services. The commission may prescribe the form of complaints filed under this section.