When I want to build a web service (client/server) with SOAP::Lite I first avoid using service method. So I constructed it like this with Data objects:

use strict;
use warnings;
use Data::Dumper;
my ($soap,$data,$result,$session);
use SOAP::Lite+trace=> 'debug';
{
  ##Connecting to the SOAP API
  $soap = SOAP::Lite->new(
              'proxy' =>('http://searchapi2.dialog.com/axis/services/D
+ialogSearchPort'),
             );
  $soap->default_ns('urn:DialogSearch');

  $data = SOAP::Data
    ->name('Session'=>\SOAP::Data->value(
                     SOAP::Data->name(Account=>'account')->type(''),
                     SOAP::Data->name(Password=>'pass')->type(''),
                     SOAP::Data->name(State=>'START_SESSION')->type(''
+),
                     SOAP::Data->name(Cost=>0)->type(''),
                     SOAP::Data->name(Atomic=>'True')->type(''),
                     SOAP::Data->name(Interrupt=>'False')->type(''),
                     SOAP::Data->name(ProcessId=>'')->type(''),
                    ),
      );
  $result = $soap->Version($data);
}
[download]

It returns:

 <ErrorMessage xsi:type="xsd:string">Invalid user id = account</ErrorM
+essage>
[download]

I had to exclude type definitions from xml because the server returned IllegalArgumentException error.
hth