SOAP API's response “Unexpected Business Object ErrorNo Action header was found with namespace”

Hello,
API’s is developed in .Net and I am calling it from PIMCORE controller.

I have pass data in XML format but getting error in response like “Unexpected Business Object ErrorNo Action header was found with namespace ‘http://www.example.org/2005/08/addressing’” ,

 $sUrl = 'http://example/Service/wsdl';
 $xml = '<soap:Envelope xmlns:soap="http://www.example.org/2003/05/soap-envelope" xmlns:sys="http://example/Service">...</soap:Envelope>';
    $headers = array(
        "Content-Type: application/soap+xml; charset=utf-8; action='http://www.example.org/2003/05/soap-envelope'",
        "Content-Length: ".strlen($xml)
        );
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL,$sUrl);
    curl_setopt($ch, CURLOPT_VERBOSE, 1);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
    curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $xml);
    $error_msg = curl_error($ch);
    print_r($sOutput);

How to resolve this error pls help.