I had this happen once - I flew to a city about 8 hours of driving time away to buy a motorcycle and landed late in the evening. My card was declined when I got gas a little after midnight and I had no cash or other card with me so I called the 24 hour support line. I had a quick conversation with a support agent explaining that I was traveling and the card needed to be reactivated right away. Within five minutes the card was working and I was back to working my way down a long chain of mistakes.