Get the label/id of current payment methods. Use this to avoid issues with differing IDs on local/staging/production. e.g. 'flat_rate:9', 'table_rate:5:5', etc.

payment_method_identifier.php

$packages    = WC()->shipping->get_packages();

foreach ( $packages[0]['rates'] as $key => $shipping_rate ) {
  dump( [ $shipping_rate->get_id(), $shipping_rate->get_label() ] );
}