Tettra admins can update your team's credit card on file or your billing email address via the Team settings->Billing page:
If you have a card on file, you should see a blue 'Update' button next to your card. If you do not yet have a card on file, adding a card will subscribe you to Tettra.
Updating you Subscription Plan Or Billing Cycle
If you are on one of our standard subscription plans you can update your plan or billing cycle (monthly or annual):