We have a new feature in the app that will allow you to update your own payment details (and view your existing details too). You will find this feature in the Settings tab, just underneath your address. If you don't see the Payment Details section, ensure that you have the latest version from the app/play store.
Please note that it may take up to 24 hours for the payment details to be updated in the app.
A full list of payment methods we currently accept can be found here.