Paying via western union can be an interesting option when it comes to overseas payments, they do have lower transaction fees in comparison to Credit card.
To transfer the money you must go to: https://www.westernunion.com/web/send-money/start
Set the receiver's country to the Netherlands and set the correct amount to the invoice amount in EUR.
Select Bank Account for how the receiver wants the money and select the desired payment method.
To finalize the payment you must fill in the receivers information. Which can be found on the invoice.