10 U.S.C. § 7592
Radiograms and telegrams: forwarding charges due connecting commercial facilities
In the operation of telegraph lines, cables, or radio stations, members of the Signal Corps may, in the discretion of the Secretary of the Army, collect forwarding charges due connecting commercial telegraph or radio companies for sending radiograms or telegrams over their lines. Under such regulations as the Secretary may prescribe, they may present a voucher to a disbursing official for payment of the forwarding charge.