nusoap (web service question)

[vocoder]

i'm trying to get information back from a web service..here is a bit of the wsdl file

<wsdl:portType name="NewsService">
- <wsdl:operation name="NewsFunction" parameterOrder="mid">
  <wsdl:input message="intf:NewsFunctionRequest" /> 
  <wsdl:output message="intf:NewsFunctionResponse" /> 

basically i should be able to pass it a certain value using "mid" and it should return to me what i want. however it's not working.
here is my code

require_once('nusoap.php');
$newsid = "1000700";
$param = array ('mid' => $newsid);
$soapclient = new soapclient('http://webserviceurl/NewsService?wsdl');

$result = $soapclient->call('NewsFunction',$param);

if ($soapclient->fault)
{
	echo "FAULT: <p>Code: {$soapclient->faultcode}<br />";
	echo "String: {$soapclient->faultstring}";
} else {
	echo "test " . $result;
print_r ($result); 
}

am i using nusoap correctly? when i use this, it tells me

FAULT: Code: ns1:Server.userException

String: java.lang.IllegalArgumentException: argument type mismatch on object "NewsService", method name "NewsFunction", tried argument types: java.lang.String

any ideas what i'm doing wrong?