Wordpress Using Ajax In Admin

//  function at top of admin page backend
add_action('wp_ajax_services_get_regions', 'services_get_regions');
function services_get_regions(){
    $group = $_GET['service_option_group'];
    $regions_table = 'v_region';

    // Array to hold data
    $bigArray = array();
    // Variable to determine the select clause
    $query = "";

    $query = "SELECT * FROM $regions_table WHERE `group` = $group ";
    $regions = $wpdb->get_results($query);

    foreach($regions as $region) {
        array_push($bigArray, $region);
    }

    header( "Content-Type: application/json" );
    echo json_encode($bigArray);

    //Don't forget to always exit in the ajax function.
    exit();
}

//Request on page that holds the page options for that tab in an include etc... <?php require_once('add_service.php'); ?>
// watch for the region type selector to change, when it does update the region list
jQuery('#new_service #service_option_group').on('change', function() {
    // Ajax query to fetch the results
    jQuery.ajax({
        type: 'get',
        url: ajaxurl,
        data: {
            action: 'services_get_regions',
            data: jQuery('#service_option_group').serialize()
        },
        dataType: 'json',
        success: function(result) {
            jQuery('#new_service #service_option_region').empty();

            // need to add the default option back in
            var option = document.createElement('option');
            var select = document.getElementById('service_option_region');
            option.text = 'Select a Region'
            option.value = -1;
            select.appendChild(option);

            // Append on the events
            for (var i = 0; i < result.length; i++) {

                // create and append each element
                var option = document.createElement('option');

                // result type will differ if its city or event
                option.text = result[i].title;
                option.value = result[i].id;

                var select = document.getElementById('service_option_region');
                select.appendChild(option);
            }
        },
        error: function(request, status, error) {
            alert(request.responseText);
        }
    })

});