Payment went through twice. Not a disaster, but the way it was handled tells you a lot about the operation.
The reference number on the letter is the only way anyone will find the file again, so it goes in the subject line of everything.
A written confirmation email after every phone call is the cheapest insurance there is.
A card that works domestically can fail on an international merchant for dull, uninteresting, entirely legitimate reasons.
Has the handling changed recently for anyone else?
If you name a shop here, say whether you are affiliated. First line is enough.
Photograph everything.
Split the order.
The published rule and the enforcement pattern are different documents. Only one of them affects you.
What do you do about the fee? Do you just pay it? Same for me with a prepaid card, unfortunately.
The cheapest option costs more once you price in the failure rate.