Apple automatically refunds the prorated amount on the original subscription after it is upgraded. Since upgrades happen immediately and start a new billing cycle beginning from the day of upgrade, the previous original subscription is refunded for the prorated amount. Is there any way to retrieve the amount that was refunded by Apple?
The transaction that was upgraded is marked with isUpgraded flag to true but the price field on it still shows the full amount and there is no App Store Server Notification that tells us how much was the refund.
How do I get the refunded amount?