This article describes how to update your billing information for Mobius Conveyor.
If you're subscribed outside of the App Store, you can change the credit card on file within the Mobius Conveyor app:
Go to Mobius Settings, then tap "Your Subscription"
Tap on "Manage Subscription"
On the following screen, select the option to update payment information.
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For in-app subscriptions (e.g. you subscribed via the Apple App Store), please follow Apple's directions here to update your payment method with Apple directly. Alternatively, you can click on this link from your iOS device to quickly see or cancel your App Store subscriptions.