The commission shall have power and authority to vary, reform, or revise, upon a fair, reasonable, and equitable basis, any obligations, terms, or conditions of any contract heretofore or hereafter entered into between any public utility and any person, corporation, or municipal corporation, which embrace or concern a public right, benefit, privilege, duty, or franchise, or the grant thereof, or are otherwise affected or concerned with the public interest and the general well-being of this Commonwealth. Whenever the commission shall determine, after reasonable notice and hearing, upon its own motion or upon complaint, that any such obligations, terms, or conditions are unjust, unreasonable, inequitable, or otherwise contrary or adverse to the public interest and the general well-being of this Commonwealth, the commission shall determine and prescribe, by findings and order, the just, reasonable, and equitable obligations, terms, and conditions of such contract. Such contract, as modified by the order of the commission, shall become effective 30 days after service of such order upon the parties to such contract.