Firstly, please double-check that the details you entered match the credit card details (eg. card number, cardholder name, CVV number, etc). If you are positive that you are using the correct credit card details and you are still getting an error, please contact us at firstname.lastname@example.org.
Please include the email address associated with your login, the specific error message that is displayed (a screenshot would be ideal), and the type of card you are using. Our customer support team will get in touch with you as soon as possible to resolve the problem.
Feel free to add any further information that might be relevant, but please do NOT send us your credit card details directly (be it via e-mail, telephonically, or via carrier pigeon). For your security, you should only enter your credit card details on the designated payment portal.