Configure SOAPAction on the Call object

factory = ServiceFactory.newInstance();
service = factory.createService(SERVICE);

call = service.createCall();
call.setOperationName(new QName(TARGET_NAMESPACE, "ConversionRate"));
call.addParameter("FromCurrency", Constants.TYPE_LITERAL_STRING, ParameterMode.IN);
call.addParameter("ToCurrency2", Constants.TYPE_LITERAL_STRING, ParameterMode.IN);
call.setReturnType(Constants.TYPE_LITERAL_DOUBLE);
call.setProperty(Call.SOAPACTION_USE_PROPERTY, Boolean.TRUE);
call.setProperty(Call.SOAPACTION_URI_PROPERTY, SOAP_ACTION);
call.setTargetEndpointAddress(ENDPOINT);

POST /CurrencyConvertor.asmx HTTP/1.1
SOAPAction: ""
Content-Type: text/xml; charset=UTF-8
User-Agent: Java/1.5.0_07
Host: www.webservicex.net
Accept: text/html, image/gif, image/jpeg, ; q=.2, */; q=.2
Connection: keep-alive
Content-Length: 260

<env:Envelope xmlns:env="http://schemas.xmlsoap.org/soap/envelope/">
<env:Header/>
<env:Body>
<ns1:ConversionRate xmlns:ns1="http://www.webserviceX.NET/">
<FromCurrency>EUR</FromCurrency>
<ToCurrency2>USD</ToCurrency2>
</ns1:ConversionRate>
</env:Body>
</env:Envelope>