Changing your payment details/card takes a few simple steps:
1. Head to Account settings (left sidebar).
2. Click Plan and Billing.
3. Switch to the Payment Method tab.
4. Finally, click New payment method to add your new card details (at this stage, you can also edit existing payment methods to remove an existing card).
ℹ️ Remember that only users with Admin or Billing permissions can modify payment details.
☑️ Checkmark a card to make it the default payment method for your account.
You're all set!
Helpful resources:

