I have a Mastercard and use it to buy books. I buy a lot of books, over $100,000 per year easily and it is not unusual for me to buy, say, $5000 worth of books on a single day from multiple vendors who may be from the USA, Canada, UK, France and other places, mostly in Europe.
The problem is that frequently this triggers Mastercard's automated fraud prevention system and they lock my card and cancel all my transactions which is extremely annoying because it damages my relationship with the book dealers and prevents me from using the card to, for example, buy gas.
I talked to a bank representative and they said the only thing they can do is to temporarily remove fraud protection from the card for up to a week. The representative said that they have no way to whitelist particular vendors or particular types of purchases.
How can I solve this problem?