If you subscribed to the Digital plan inside the mobile app, your membership is billed through the App Store, and Apple handles the billing side of your subscription. That means plan changes, cancellation, and payment fixes happen in Apple's subscription settings, not in ENCODED.
How to tell how you're billed
Open your membership details in the app or in My account on the web. If your plan is billed by Apple, you'll see your renewal date followed by "billed through the App Store. To change or cancel your plan, open Settings on your iPhone and tap Subscriptions." If you don't see that note, you're billed on the web (see below).
Changing or cancelling your plan
Open Settings on your iPhone.
Tap Subscriptions.
Select ENCODED, then change or cancel your plan.
Changes made in ENCODED's own account screens are not possible for App Store billed memberships: the app and My account show your plan, but the subscription itself is managed by Apple.
Fixing a payment issue
Payment problems with an App Store subscription, such as an expired card, are also fixed in Apple's subscription settings, in the same place as above. ENCODED cannot update the payment method Apple has on file.
If you're billed on the web
Members who purchased on the web manage everything in My account on the web: changing plans, switching between Monthly and Annual, cancelling, and updating payment details.