I would like to pay by a different credit card

Joseph, Have a look @ this article (https://support.avg.com/SupportArticleView?urlname=How-can-I-change-my-payment-details).
AVG Guru

Hi Joseph,
Please note that your payment details are stored only if you sign up for automatic renewals during the purchase. For security reasons, they are stored by the payment gateway provider, not in the AVG internal database. Therefore AVG Customer Services members can't verify or change your card number in our system.
I can disable you autorenewall if enabled and you can buy it using different card.
Thanks

Joseph, Have a look @ this article (https://support.avg.com/SupportArticleView?urlname=How-can-I-change-my-payment-details).
AVG Guru