So now, I wait. I call the helpline, recite my mother’s maiden name, and prove my identity to a stranger. “Yes, I really did try to buy that plane ticket.” “No, I don’t live in another country.”

If the app doesn’t resolve it, call the number on the back of your card (or the general customer service line). Say "My card is blocked" to the automated system. Do not shout "representative" immediately. Most banks have an automated unblocking system that only requires you to: