Been through quite a few forums, but still havent managed to create a relationship!

PHP Code:
$user_auth = array( 
'user_auth' => array( 
    'user_name' => $username, 
    'password' => $password, 
    'version' => '0.1' 
), 
'application_name' => 'soapContactcapture'); 
          
$result_array = $soapclient->call('login',$user_auth); 
$session_id = $result_array['id']; 
$user_guid = $soapclient->call('get_user_id',$session_id);         

$set_entry_params = array( 
                    'session' => $session_id, 
                    'module_name' => 'Contacts', 
                    'name_value_list'=>array( 
                            array('name'=>'first_name','value'=> $firstName), 
                            array('name'=>'last_name','value'=> $lastName),
                            array('name'=>'email1','value'=> $email),
                            array('name'=>'primary_address_postalcode','value'=> $postcode),
                            array('name'=>'phone_work','value'=> $phone),
                            array('name'=>'event_id_c','value'=> $event),
                            array('name'=>'event_date_c','value'=> $eventDate),
                            array('name'=>'assigned_user_id', 'value'=> $assigneduid)
                    )
); 
$result = $soapclient->call('set_entry',$set_entry_params);
$bookingid = $result['id'];

$set_relationship_params = array(
'session' => $session_id,
            'module_name' => 'leads',
            'module_id' => $leadid,
            'link_field_name' => 'contact_id',
            'related_ids' => array($bookingid)
        );
$link = $soapclient->call('set_relationship',$set_relationship_params); 
the output is:
HTML Code:
array(3) { ["number"]=> string(2) "20" ["name"]=> string(21) "Module Does Not Exist" ["description"]=> string(43) "This module is not available on this server" }
but Leads and Contacts exist as they are standard modules?

what am i doing wrong?