If you're the super-admin user (the user to which the account is linked), you'll see an extra section in the settings menu: Billing:
Here you can:
1. Edit your account information
2. Edit your payment method
3. Edit your billing information
4. See your payment history (and download your pdf invoices)
5. Edit your subscription plan (you won't be able to change your plan until after your trial has ended and you've converted to a paid subscription. You can, however, change the number of users in your plan while in trial, by using the "Change the number of available users in your pricing plan to..." in the app's billing area.
6. Cancel your subscription