Like nearly everyone, you have sooner or later faced problems with your credit card company's fraud department: they exist to protect you from unauthorized charges, but (fortunately, in a sense) they are wrong in most cases, and it is simply you (or another authorized user) who has made more purchases than usually, or made purchases from another geographical location. Whatever triggered the alert, one common effect is that purchases you try to make end up being blocked; in the case of the iTunes Store, you will no longer be able to buy anything until you fix the problem; on your iPad (but this can occur on your iPhone, iPod touch, or from iTunes itself), you may receive the "Verification Required" error message, described as follows: "Before you can make purchases, you must tap Continue, then verify your payment information". Read the rest of this tutorial to learn how to correct this problem.
Follow these steps to correct billing information errors on your iPad:
If all your payment information and credit card details are correct, as well as billing address, first check with your bank to make sure that they are not blocking the charges thinking it is a fraudulent transaction.
If this didn't take care of your payment issue, contact iTunes customer service.