Managing your Radiant Camera subscription is simple and fully handled through the App Store
Canceling your subscription
To cancel your subscription and prevent future payments while continuing access for the remainder of your paid period, follow Apple’s instructions:
iOS/iPadOS subscription cancellation guide
Updating your payment method
To update your payment method for your Radiant Cameras subscription, see Apple’s guide here:
iOS/iPadOS payment method guide
Refunds
To request a refund, you can contact Apple here: https://support.apple.com/billing