c# ile web servisine bağlanırken security header hatası

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:oper="Proxy"> 
     <soap:Header/> 
     <soap:Body> 
        STUFF 
     </soap:Body> 
  </soap:Envelope>

 
  <soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:oper="webservis adresi"> 
    <soap:Header> 
    <wsse:Security 
     xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"> 
     <wsse:UsernameToken> 
      <wsse:Username>USERNAME</wsse:Username> 
      <wsse:Password>PASSWORD</wsse:Password> 
     </wsse:UsernameToken> 
    </wsse:Security> 
   </soap:Header> 
     <soap:Body> 
        REQUEST 
     </soap:Body> 
  </soap:Envelope>