The Commission shall have continuing supervisory control over the terms and conditions of such contracts and arrangements as are herein described so far as necessary to protect and promote the public interest. The Commission shall have the same jurisdiction over the modification or amendment of contracts or arrangements herein described as it has over such original contracts or arrangements. The fact that the Commission shall have approved entry into any such contract or arrangement shall not preclude disallowance or disapproval of payments made pursuant thereto in the future, if upon actual experience under such contract or arrangement, it appears that the payments provided for, or made, were, or are, unreasonable. Every order of the Commission approving any such contract or arrangement shall be expressly conditioned upon the reserved power of the Commission to revise and amend the terms and conditions thereof, if, when and as necessary to protect and promote the public interest.