Further to my reply above, I communicated with my ISP to obtain more detailed info to share with you. Here is what I got: 
They have provided me a php example of the code that would fill out the header according to SOAP standards. Curl libraries are used. This is to illustrate what needs to be done: 
$tuCurl = curl_init(); 
curl_setopt($tuCurl, CURLOPT_URL, "http://example.com/path/for/soap/url/"); 
curl_setopt($tuCurl, CURLOPT_VERBOSE, 0); 
curl_setopt($tuCurl, CURLOPT_HEADER, 0); 
curl_setopt($tuCurl, CURLOPT_POST, 1); 
curl_setopt($tuCurl, CURLOPT_SSL_VERIFYPEER, 1); 
curl_setopt($tuCurl, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt($tuCurl, CURLOPT_POSTFIELDS, $data); 
curl_setopt($tuCurl, CURLOPT_HTTPHEADER, array("Content-Type: text/xml","SOAPAction: \"/soap/action/query\"", "Content-length: ".strlen($data))); 
You may also do a search for SOAP BY EXAMPLE to find examples using other languages. I know you need .NET example. Going through some of the exmaples on the web, I found out that, to do a search request to Google using a client software, it is also necessary to use a similar SOAP standard which is described in Google API documentation. 
I hope this helps. 
Kind Regards, 
Ali