Ok, we figured it out. Dad was a victim of identity theft and the bank locked his credit cards and account. The bank caught it right away. It all got resolved now and he has a new credit card and was able to order without any problems today. I'm glad it got caught in time before there was any damage done to dad's account. This is so scary!!! But I'm relieved now that everything is OK.
Again, thank you for your advise. It turned out to be something different but I would have never even considered that... But I guess it's more and more common these days and you really have to pay attention to your credit cards charges.