For this, it depends on if you have an Android or iOS device.
If you have an iOS device, take a peek in the Settings of the app. Next, find the section named "Membership“ and tap on it to open it. In there, you will see an overview of your current payment information. By tapping on "Change payment info“, you can edit your payment data.
However, if you have an Android device, it won't be possible at this time to change it in the app. Please email us to firstname.lastname@example.org for a more information!