To purchase Facebook Credits within a game, click on any premiumitem in an app's store or choose to purchase in-game cash or coins. Thepurchase process may be different in different games but in all Facebook gamesyou will be able to use your Facebook Credits. Additionally, you can purchaseFacebook Credits from the Payments tab in your account. From this tab you canclick the Buy More link to begin the purchase process.
If you choose to purchase credits from the 'Buy More' link the process lookslike the following:
You will be prompted to select your desired payment method in the first step.In the second step (below) you can choose your desiredamount of Facebook Credits to purchase.Currently we accept the following types of credit/co-brandeddebit cards for Facebook Credit purchases: Credit cards: Visa, MasterCard, AmericanExpress, and Discover, JCB Co-branded debit cards: Visa, MasterCard, andAmerican Express. If you still face the problem then, first verify that thecredit card number, address, and other payment information are correct beforeretrying your purchase. If you are still experiencing difficulty, and fill outthis form here: http://www.facebook.com/help/contact_us.php?id=137574362977954
.Hope this will help you. Good Luck.