Hide shipping rates when free shipping is available with certain amount

/**
 * Hide shipping rates when free shipping is available.
 * Updated to support WooCommerce 2.6 Shipping Zones.
 *
 * @param array $rates Array of rates found for the package.
 * @return array
 */
function allaround_hide_shipping_when_free_is_available( $rates ) {

    // Here your free shipping rate Id
    $free_shipping_rate_id = 'free_shipping:6';

    // When your Free shipping method is available
    if ( array_key_exists( $free_shipping_rate_id, $rates ) ) {
        // Loop through shipping methods rates
        foreach ( $rates as $rate_key => $rate ) {
            // Removing "Flat rate" shipping method
            if ( 'flat_rate' === $rate->method_id ){
                unset($rates[$rate_key]);
            }
        }
    }
    return $rates;
    
}
add_filter( 'woocommerce_package_rates', 'allaround_hide_shipping_when_free_is_available', 100 );