As per the OOMPH Billing Terms, we do not offer refunds or credits for unused subscription periods or accidental purchases.  OOMPH subscriptions are In-App Purchases and therefore are purchased from and billed by the respective App Store (such as the Apple App Store), not by us.  An In-App Purchase is subject to the terms and conditions specified by that App Store provider.  Therefore, any payment-related issues with that App Store must be taken up with that provider directly.