You can securely update your payment information from within your online account.
To update your billing information:
Log in here then look in the main navigation and click on Account > Billing where you'll find Payment Methods noted. To edit your current payment information, click on the pencil icon to the right of your credit card's last 4 digits.
Add a secondary payment method:
You can add one additional form of payment should you need to switch payment between two different credit cards. To add an additional credit card, click on the "+ Add Payment Method" button below your credit card information and complete the input form.
For more information try:
Why can't I update my credit card?