You can subscribe to OnSong either through the App Store or through the OnSong website. In general, when you cancel a subscription you continue to retain access to the subscription through the term of the last payment. For instance, if you had paid for an annual subscription and cancel that subscription six months in, you will not be charged for the following year, but you will continue to have access to subscription features for the remaining six months. If you require a refund, the policies surrounding cancellation differ due to the payment being processed by either Apple Inc. or OnSong LLC.
If you've subscribed to or purchased OnSong through the App Store, you'll need to request a refund directly from Apple. This is because all purchase transactions and provisioning are controlled by Apple and are not accessible to the developers of apps. Typically you would need to contact Apple within 90 days to request a refund. If you have trouble, you will need to contact Apple support as developers do not have the means to issue App Store refunds. These transactions are made under the Apple's App Store refund policy.
If you've subscribed through the OnSong website for either an OnSong solo or group subscription, you can obtain a prorated refund when you cancel your subscription as long as you choose to terminate the subscription immediately. If you need additional assistance, please contact OnSong billing support. Refunds are processed immediately but could take a few days to appear on your credit card or bank statement.