We all hate bank fees.
When you pay your Haystack payment with your credit card, Haystack uses Stripe to process these transactions. Haystack set up Stripe account to include all fees and charges as part of these payments so any costs of domestic or international fees are covered by Haystack and will not be added to your monthly or annual payment.
In some rare occasions you will notice a separate small 'international transaction fee' showing up on your credit card bill (on top of the Haystack payment). The small fee you see in your bank statement is your bank's fee which it charges you just because Haystack is registered in Australia even though we've taken care of all the associated international transaction fees for them already (it costs your bank $0).
If your bank is one of these rare cases, please note that this is a legacy cost which most banks have stopped charging their clients, and I urge you to contact your bank and ask them to remove these charges from your account - as nearly any other bank will not charge you these fees (after all - Haystack already covered these fees, and the bank is basically double dipping by also charging you).
This fee is not visible to Haystack and therefore it does not show up on your Haystack invoice - it is a separate charge by your bank, and your bank should be able to provide any necessary documentation for it.