Next time I hear someone complain about high interest rates on credit cards in the U.S., I’ll be sure to pass this story along to them. Wal-Mart de Mexico, which is known as Walmex, plans to ramp up its credit-card business in Mexico by the end of the year, according to Bloomberg sources. All told, the bank plans to issue more than 100,000 cards. The cards will have annual percentage rates that range from 59% to 75%. Ouch. Amazing interest rates, no? Consider this: that’s down from 90%!

American Express is very hip to this game, by the way. Paypal purchases are always scrutinized by American Express. They’re scrutinized because it’s so easy to do what I’ve just described. Small purchases won’t likely gain anyone’s attention at American Express, but you can bet your bottom dollar that big purchases won’t go unnoticed.

American Express, once it has flagged your account, wants to know two things: one, are you essentially doing a cash advance or balance transfer? And, two, are you broke? Indeed, if you are doing these kinds of sham transactions, you’re likely strapped for cash. If you’re strapped for cash, and doing these kinds of deals, then you’re likely a high-risk customer to American Express. If you’re a high risk to American Express, it’s going to reduce your limit substantially or cancel your card altogether.

If you’re going to do these kinds of Paypal transactions, don’t use American Express to do it. They’re on top of the game when it comes to this stuff. Better still, just don’t do it at all. Indeed, this is not the credit environment in which to test the cards companies’ computer systems.