Update shipping legacy flat rate label text when shipping cost ( Zero )”0″

function wc_update_flat_rate_label( $rates, $package ) {
if($rates[‘legacy_flat_rate’]->cost == 0){
$rates[‘legacy_flat_rate’]->label = “Free shipping”;
}
return $rates;
}
add_filter( ‘woocommerce_package_rates’, ‘wc_update_flat_rate_label’, 10, 2 );