You can update your payment method at any time through the billing portal. This allows you to add a new card and set it as your primary or backup payment option.
Go to Settings.
Navigate to Plans & Billing.
Click Manage.
A billing portal will open in a new window. Click Payment methods.
Click Add New.
Enter your card details and confirm. Set the new payment method as Primary or Backup.
Setting a payment method as Primary will replace your current default payment method. On the other hand, Backups come handy when your primary payment fails.