I had it down to a science, I knew the direct number to their fraud dept and I knew when I should place my call so that I'd usually be connected at just the right time to get the charge authorized with enough time to avoid the website session from timing out, although sometimes I'd have to start over. Eventually, air canada added a timeout popup which helped prevent this.
I tried everything to get BoA to fix this (escalating calls, writing letters, etc). By the end, I gave up and just accepted it when they "put a note" on my account so this "would never happen again". This went on for over 2 years. Thankfully my company switched our cards to another bank and I never had this problem again.
Alas, a human also saw the transaction, failed to read the note or look in the history and locked the card up anyway.
We don't see this problem with banks in any other country (not do I ever have the problem in reverse, buying goods and services from foreign websites with my Australian credit card).
I say this as an American who has never lived outside the US but who deals with international clients regularly: the US seems uniquely inclined (in my experience) to think that everything they need falls within their borders, and everything outside their borders should be treated with suspicion. I've never had a German client want to block all traffic from South Africa. That's just an observation, I make no judgements as to why that is.
I did have an American university for a client who said "we cannot block or otherwise discriminate traffic from anywhere, since we have students or staff in every country outside of North Korea" which is a refreshing outlook IMO.
FWIW, I paid with AMEX (using Stripe not PayPal) and it went through right away.
For what it is worth, Fastmail has been as good as they can be with this issue, but they're at the mercy of my bank as much as I am.
This, to me, represents the worst that banking fraud protection has to offer. Just yesterday I (from the USA) tried to purchase a software license for a tool I've been using the free version of for a long time. My card was declined, so I used my American Express. About two hours later, I got a call from my bank's fraud department saying they had blocked a transaction to the UK for fraud prevention, and disabled my card to protect me. Apparently the bank (a small US-based bank) block any transaction in the UK as it's a "high risk country"... I'm sorry, but this is the Internet. No one cares where the company is located, and I have no way of knowing beforehand that the payment is processed by Stripe US or Stripe UK. Blocking entire countries for fraud prevention is a really lazy way of doing fraud prevention.
But I've even seen worse at another bank. My area of the US doesn't have Publix grocery stores. Apparently this bank considered shopping at Publix to be unacceptable risk when I was traveling for work, and disabled my debit card because of this. Stopping at Walgreens beforehand and getting dinner the night before wasn't suspicious though.
Bank fraud is a hard problem, and taking lazy solutions doesn't solve that problem. It just hurts customers and hurts businesses.