No remuneration on account of any services rendered on behalf of any claimant in connection with any claim filed with the Commission under this subchapter shall exceed 10 per centum of so much of the total amount of such claim, as determined under this subchapter, as does not exceed $20,000, plus 5 per centum of so much of such amount, if any, as exceeds $20,000. Any agreement to the contrary shall be unlawful and void. Whoever, in the United States or elsewhere, demands or receives on account of services so rendered, any remuneration in excess of the maximum permitted by this section, shall be fined not more than $5,000 or imprisoned not more than twelve months, or both.