It sounds like the billing address you entered might be incorrect. It has to match the address showing on your credit card statement. When you are on the payment page, make sure to click on "Uncheck this box if your billing address is different from shipping address" and enter the correct billing information here.
If this does not help, the issue must be with the card itself. If this does not resolve the issue, please try one of the following:
• Try using a different internet browser
• Try clearing the cache of the current one
• Try placing your order from a different device, if you are currently using your mobile phone / tablet If none of these works, please try using a different payment method or PayPal account.
If you are still having trouble after trying these options, please contact us at firstname.lastname@example.org, and we would be happy to assist you further.