static void Main(string[] args)
        {
            Execute();
            Console.ReadLine();
        }
        public static void Execute()
        {         
            HttpWebRequest request = CreateWebRequest();
            ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
            
            request.Credentials = new NetworkCredential("test", "test");
            XmlDocument soapEnvelopeXml = new XmlDocument();
            soapEnvelopeXml.LoadXml(@"<SOAP-ENV:Envelope xmlns:SOAP-ENV=""http://schemas.xmlsoap.org/soap/envelope/"">
  <SOAP-ENV:Header/>
  <SOAP-ENV:Body>
    <ns5:GetSignatureMode xmlns:ns5=""http://ws.gematik.de/conn/SignatureService/v7.5""  xmlns:ns3=""http://ws.gematik.de/conn/ConnectorCommon/v5.0""  xmlns:ns6=""http://ws.gematik.de/conn/ConnectorContext/v2.0""  xmlns="""">
      <ns3:CardHandle>test</ns3:CardHandle> (1)
      <ns6:Context> (2)
        <ns3:MandantId>test</ns3:MandantId>
        <ns3:ClientSystemId>test</ns3:ClientSystemId>
        <ns3:WorkplaceId>test</ns3:WorkplaceId>
        <ns3:UserId>test</ns3:UserId>
      </ns6:Context>
    </ns5:GetSignatureMode>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>");
            
            using (Stream stream = request.GetRequestStream())
            {
                soapEnvelopeXml.Save(stream);
            }
            using (WebResponse response = request.GetResponse())
            {
                using (StreamReader rd = new StreamReader(response.GetResponseStream()))
                {
                    string soapResult = rd.ReadToEnd();
                    Console.WriteLine(soapResult);
                }
            }
        }
       
        public static HttpWebRequest CreateWebRequest()
        {
            HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(@"https://192.168.3.100:443/webservices/authsignatureservice");
            webRequest.Headers.Add(@"SOAPAction", "http://ws.gematik.de/conn/SignatureService/v7.5#GetSignatureMode");
            webRequest.ContentType = "text/xml; charset=UTF-8";
            webRequest.Timeout = 50000;
          //webRequest.ContentLength = 2070;
            webRequest.Accept = "text/xml";
            webRequest.Method = "POST";
            webRequest.Credentials = new NetworkCredential("test", "test");
            return webRequest;
        }
 

 

soapEnvelopeXml.LoadXml(@"<SOAP-ENV:Envelope xmlns:SOAP-ENV=""http://schemas.xmlsoap.org/soap/envelope/""
xmlns:m0=""http://ws.gematik.de/conn/ConnectorContext/v2.0""
xmlns:m1=""http://ws.gematik.de/conn/ConnectorCommon/v5.0""
xmlns:m2=""http://ws.gematik.de/conn/CardServiceCommon/v2.0"">
<SOAP-ENV:Body>
<m:GetCards
xmlns:m=""http://ws.gematik.de/conn/EventService/v7.2""
mandant-wide=""false"">
<m0:Context>
<m1:MandantId>xx</m1:MandantId>
<m1:ClientSystemId>xx</m1:ClientSystemId>
<m1:WorkplaceId>xx</m1:WorkplaceId>
</m0:Context>
</m:GetCards>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>");