这个PHP函数对于Woocommerce Cart有什么问题？

I created a function for adding a fee to the Woocommerce cart. It works partially, but displays the lowest fee. It just ignores the condition of <= 550 and the highest fee. Does anyone have an idea how to fix this?

function verzendkosten( $cart_object ) {

    global $woocommerce;
    $laag = 37.50;
    $hoog = 57.50;
    $vala = 550.00;
    $prijs = $woocommerce->cart->total;

    if($prijs <= $vala) {

        $woocommerce->cart->add_fee( 'Verzendkosten', $hoog, true, 'standard' );
    }

    if($prijs > $vala) {

        $woocommerce->cart->add_fee( 'Verzendkosten', $laag, true, 'standard' );
    }
}

add_action( 'woocommerce_cart_calculate_fees', 'verzendkosten' );