How to call a SOAP function to send Drupal user data to a SOAP server?
You say you use the wsclient SOAP binding but your code doesn't use it. Instead, your code uses a direct query to the PHP SOAP interface. 

This thread discusses the difference between the two binding and which one is preferrable. 

From the module's readme file:


You can create web service descriptions in code, see for example
wsclient_examples.module
You can easily invoke web services by loading the description and executing
an operation (the operation name can be used a dynamic method name):

$service = wsclient_service_load('google');  
$result = $service-&gt;translate('Hallo Welt', 'de|en');