Hi Idango,
From looking into this, it doesn't seem like there is an option to directly cancel or credit an App Usage Record. Once a UsageCharge has been created and accepted, it cannot be cancelled. It can only be adjusted by creating a separate `ApplicationCredit` event.
However, you should note that usage charges are billed separately from recurring application charges and one-time application charges. If an app doesn't use the full amount of its usage charge, then the unused amount can't be refunded. If you've made a mistake in a usage charge, you should create a new usage record with the corrected price.
