To access your payment settings, click on your avatar in the top corner of the screen and click "Account" in the dropdown.
In your Account settings, you will see "Billing" at the bottom.
To change your plan, click "Change Plan" and you can choose to change the plan you're currently on.
You can update your payment method as well by clicking "Update Payment Method".
Your credit card details are stored in Stripe, a highly reputable third-party payment provider, not in Knarr. We do not ever store your credit card details and everything is handled in Stripe.
If you have any issues or difficulties with your payments, please email firstname.lastname@example.org