woocommerce-modify-orderby.php

<?php
// Modify the default WooCommerce orderby dropdown
//
// Options: menu_order, popularity, rating, date, price, price-desc
// In this example I'm removing price & price-desc but you can remove any of the options
function my_woocommerce_catalog_orderby( $orderby ) {
	unset($orderby["price"]);
	unset($orderby["price-desc"]);
	return $orderby;
}
add_filter( "woocommerce_catalog_orderby", "my_woocommerce_catalog_orderby", 20 );