从ajax调用中检索值

I have seen many topics like mine but I can't resolve my problem who seems so simple.

I have this function in JS :

function displayFullDesignation(id, select) {
            var fullDesignation = $('option:selected', select).data('idacc');
            var myId = parseInt(fullDesignation);
            $.ajax({
                url: '<?php echo $this->url(array('controller' => 'catalog', 'action' => 'fullname'));?>',

                type: 'POST',
                datatype: 'json',
                data: {'id': myId},
                success: function(data) {
                if(data.success){
                    console.log(data.success);
                }
        }
    }); 

    return fullDesignation;
}

And in my controller :

 /**
 * AJAX Action
 */
public function fullnameAction($params) {

    $ajaxContext = $this->_helper->getHelper('AjaxContext');
    $ajaxContext->addActionContext('fullname', 'json')->initContext();

    $response = array();
    $params = $this->getAllParams();

    $listModels = Application_Model_Catalog_Accessory_List::getDesignationComplet($params['id']);

        $response['success'] = true;
        $response['aaData'] = $listModels;


    $this->getHelper('json')->sendJson($response);

}

I don't know why I can't get anything from this ajax call. If I try to do a var_dump inside my function, it does nothing at all so I think that my call isn't good, but I have other calls who work like this.

What am I doing wrong please ?

And if I do a console.log of 'data', it gives me HTML. data.success gives me undefined.

Thanks !!