Do not access order properties directly

E.g instead of `$order->id()` you can use `$order->get_id()`

Warning stacktrace:

`[02-May-2022 17:37:00 UTC] total was called incorrectly. Order properties should not be accessed directly. Backtrace: require('wp-blog-header.php'), require_once('wp-includes/template-loader.php'),`