Remove free shipping in WooCommerce if a coupon is applied at checkout
add_filter( 'woocommerce_shipping_packages', function( $packages ) {
$applied_coupons = WC()->session->get( 'applied_coupons', array() );
if ( ! empty( $applied_coupons ) ) {
$free_shipping_id = 'free_shipping:2';
unset($packages[0]['rates'][ $free_shipping_id ]);
}
return $packages;
} );