Before starting, I know these errors mean that I had to define the FinalBookingDate property, but just keep reading and you will understand my point.
URL: http://bestbuyhotel1.cangooroo.net/ws/2013/ClientBackOffice_b.asmx?op=getBookingList
I first tested SoapUi and I managed to get the list I need:

And in php I can get this answer: 
SoapClient from php:
$params = array('soap_version' => SOAP_1_2, 'compression' => SOAP_COMPRESSION_ACCEPT | SOAP_COMPRESSION_GZIP, 'encoding'=>'UTF-8', 'trace' => 1, 'exceptions' => true, 'cache_wsdl' => WSDL_CACHE_NONE, 'features' => SOAP_SINGLE_ELEMENT_ARRAYS);
$client = new \SoapClient('http://bestbuyhotel1.cangooroo.net/ws/2013/ClientBackOffice_b.asmx?wsdl', $params);
And then, the code to retrieve the data:
$query = array(
'InitialBookingDate' => '2015-01-20',
'ServiceTypes' => array('eServiceType' => 'HOTEL')
);
$args = new \stdClass;
$args->credential = new \stdClass;
$args->credential->UserName = $conn['userPass']['usr'];
$args->credential->Password = $conn['userPass']['pass'];
$args->searchBookingCriteria = new \stdClass;
$args->searchBookingCriteria->InitialBookingDate = '2015-01-20';
$args->searchBookingCriteria->ServiceTypes = new \stdClass;
$args->searchBookingCriteria->ServiceTypes->eServiceType = 'HOTEL';
$data = $conn['client']->getBookingList($args);
print_r($data);
exit;
, $args getBookingList, , , ( ) . , , , , -, .
: - SoapClient, ? SoapUI ? ?
: SoapUI , https://www.evernote.com/shard/s14/sh/fb5ac276-8147-4e09-95bb-afa0be66d7a6/d273441c74186bf1e600b42ab3303899/deep/0/SoapUI-5.0.0.png