Show Hide Shipping Methods Based on Cart Totals in WooCommerce https://wpsites.net/wordpress-tutorials/show-hide-shipping-methods-based-on-cart-totals-in-woocommerce/

conditional-shipping-woocommerce.php

add_filter('woocommerce_package_rates', 'switch_flat_rate_based_on_total_v3', 10, 2);
function switch_flat_rate_based_on_total_v3($rates, $package) {

    $cart_total = WC()->cart->get_cart_contents_total();
    $flat_rate_5 = 'flat_rate:5'; // ID for flat rate 5
    $flat_rate_7 = 'flat_rate:7'; // ID for flat rate 7

    if ($cart_total > 150) {
        if (isset($rates[$flat_rate_5])) {
            unset($rates[$flat_rate_5]);
        }
    } else {
        if (isset($rates[$flat_rate_7])) {
            unset($rates[$flat_rate_7]);
        }
    }
    
    return $rates;
}