Please check that you have filled in the 16 numbers of your credit card, without spaces or dashes.
Also, make sure you entered the security code in the CVV box. These are the last 3 digits on the white stripe at the back of your card.
You must also accept our terms and conditions in order to validate your payment.
Please try to with another card or try paying with Paypal. You do not need a Paypal account to pay with Paypal, you can simply pay with your credit card.
If your payment is still refused, please contact your bank and indicate them your date and time of payment trial and they should be able to look into the reason.