Quite. Good for points harvesting.....because a lot of my work travel is with BA I’ve got a BA Amex equivalent, tops the miles up nicely and also means I get a ‘free’ (have to pay taxes obviously) companion air ticket once a year (any destination/class) which is a huge benefit.
Credit Card "Fraud"
The companies flex their thresholds/criteria all the time, and real-time, and have done for at least 30 years. If the crims knew the criteria were fixed, it would be very easy to work within them. Variations are applied through transaction limits, retailers...
Suspect your card has been cloned, and they have detected multiple, obviously fraudulent uses so they have blocked it. Not particularly unusual but they’d usually explain this if you could actually speak to an adult.