Using nusoap is pretty easy once you see how it works.
The webservice should request an XML formatted document:
<xml>
<request>
<field1>some data</field1>
<field2>some data</field2>
<field3>some data</field3>
</request>
</xml>
Yours will be:
$XMLSTR = "<xml>
<person>
<FistName></FirstName>
<LastName ></LastName >
<UserTypeCode ></UserTypeCode >
<HomePhone ></HomePhone >
<CellPhone ></CellPhone >
<PasswordHash ></PasswordHash >
<PasswordSalt ></PasswordSalt >
</person>
</xml>";
Then you need to instantiate the nusoap
$oClient = new soapclient('this is the webservice url?wsdl','wsdl'); // DO NOT FORGET TO ADD THE ?wsdl TO THE END OF THE URL
Then, you need to create an array of parameters, this is where you send the XML string and any other data that's required. From what is provided, I can not tell, but if you go to the webservice URL, you will be able to see the examples. .NET webservices usually highlite the parameter names in a dark blue
$PARAMS = array(
'XML_STRING_VAR_NAME'=>$XMLSTR
);
Then you send your webservice call:
$RESPONSE = $oClient->call('Add',$PARAMS );
I'm using the 'Add' as the function your are calling.
Hope this helps!