Amex is very weird with flagging spending. I usually do around 2500 a month, but when I went on vacation and tried to pay something for 50 USD for a street vendor, my card got declined and I had to call in. I've also had the incident where I was spending a minimal amount at bergdorf and I also got flagged, yet when I did my downpayment for my car with my amex I didn't get flagged