add_filter( 'wcfm_is_allow_view_customer', function( $allow ) {
    global $_POST;

    if ( ! check_ajax_referer( 'wcfm_ajax_nonce', 'wcfm_ajax_nonce', false ) ) return $allow;

    if (isset($_POST['controller']) && 'wcfm-enquiry' == $_POST['controller']) {
        $allow = false;
    }

    return $allow;
} );