I had a similar issue recently with my citibank card. They didn't call and I can't remember if I even got a text, I just tried to log into my online banking and couldn't access my account. My card was blocked as well. I rang up to find out what was going on, it turned out that they were alarmed by "unusual spending" on my account. Asking what on earth this could be, seeing as I have accessed this account in rural towns in India, Antigua, Nepal etc.... Turns out it was a $2.99 purchase for a PDF Lonely Planet chapter. Perplexing.