How to resolve the Internal Server Error with my custom components calendar in Joomla 4?

Question

I try to make a custom calendar in my custom component in Joomla 4. For that I write a code who connect to a database and retrieve the data. For that I have 3 files : default.php, ReservationController.php and AjaxReservationController.php. When I change the months in my calendar, I get an Internal Server Error and when I go to the url who are in my default.php I get the Invalid Class Controller : ReservationController.

Here is the code in default.php :

let calendarAvailabilities = {};
                        let days;

                        let periods = jQuery.get( "index.php?option=com_skydivespa&task=reservationcontroller.getClosingDays", {"month": cal.getMonth(), "year": cal.getYear()},
                            function( data ) {
                                days = JSON.parse(data);
                                console.info(data);
                            });

Here is the code in ReservationController.php :

namespace Zzam\Component\SkydiveSpa\Site\Controller;

use ...

class ReservationController extends BaseController {

    // Other code
 
    public function getClosingDays()
    {
        try {
            $input = Factory::getApplication()->input;
            $month = $input->get('month');
            $year = $input->get('year');

            // Validate and process the month and year values as needed

            $ajaxController = new AjaxReservationController();
            $ajaxController->getClosingDays($month, $year);
        }  catch (Exception $e) {
            // Handle the exception
            echo 'Error occurred: ' . $e->getMessage();
        }

    }

And here is the code in AjaxReservationController.php :

namespace Zzam\Component\SkydiveSpa\Site\Controller;

use ...

class AjaxReservationController extends BaseController {

    // Other code
    
    public static function getClosingDays($month, $year)
    {
        try
        {
            //$month = sprintf("%02s", Factory::getApplication()->input->get('month'));
            //$year = Factory::getApplication()->input->get('year');


            // Get a database object.
            $db = Factory::getContainer()->get('DatabaseDriver');
            $query  = $db->getQuery(true);

            $query->select('p.date_start, p.date_end, p.mon, p.tue, p.wed, p.thu, p.fri, p.sat, p.sun');
            $query->from($db->quoteName('#__skydive_periods') . ' AS p');
            $query->where('p.type = "PERIOD_r"');
            $query->where('p.published = 1');
            $query->where('( (MONTH(p.date_start) = '. $month .' AND YEAR(p.date_start) = '. $year .') OR (MONTH(p.date_end) = '. $month .' AND YEAR(p.date_end) = '. $year .') )');
            $db->setQuery($query);
            $periods = $db->loadObjectList();

            $document = Factory::getApplication()->getDocument();
            $document->setMimeEncoding('application/json');
            echo new JsonResponse($periods);
            Factory::getApplication()->close();
        }
        catch(Exception $e)
        {
            return new JsonResponse($e);
        }
    }

I don't know what cause this error. Can you help me ?

EDIT : I added the namespace and class definition. I also tried to change the call to call directly AjaxReservationController but I have the same problem