<message version="1.0" system="avs/3">
  <header>
    <client>999</client>
    <avs3-sales-organization>9999</avs3-sales-organization>
    <avs3-service-provider>123</avs3-service-provider>
  </header>
  <body>
    <subscription-order>
      ...
    </subscription-order>
  </body>
</message>