Snippet to hide WooCommerce shipping rates when Free shipping is available in the cart. Supports PluginHive Shipping Plugins: https://www.pluginhive.com/product-category/woocommerce-plugin/woocommerce-shipping/

functions.php

add_filter('woocommerce_package_rates', 'xa_hide_shipping_rates_when_free_is_available', 10, 2);

function xa_hide_shipping_rates_when_free_is_available($rates, $package)
{
	global $woocommerce;
	$version = "2.6";
	if (version_compare($woocommerce->version, $version, ">=")) {
		$new_rates = array();
		foreach($rates as $key => $rate) {
			if ('free_shipping' === $rate->method_id || 'local_pickup' === $rate->method_id) {
				$new_rates[$key] = $rates[$key];
			}
		}

		return empty($new_rates) ? $rates : $new_rates;
	}
	else {
		if (isset($rates['free_shipping'])) {

			// Below code is for unsetting single shipping method/option.
			$free_shipping = $rates['free_shipping'];
			if (isset($rates['local_pickup'])) {
				$local_pickup = $rates['local_pickup'];
				$rates = array(); // Unset all rates.
				$rates['local_pickup'] = $local_pickup; // Restore local pickup.
				$rates['free_shipping'] = $free_shipping; // Restore free shipping rate.
			}
			else {
				$rates = array(); // Unset all rates.
				$rates['free_shipping'] = $free_shipping; // Restore free shipping rate.
			}
		}
	}

	return $rates;
}