Apple:
Unfortunately, we don’t have the ability to issue refunds. Please visit https://support.apple.com/HT204084 for instructions on how to request a refund directly from Apple.
Refund eligibility might vary by country or region. See the Apple Media Services Terms and Conditions for details. In countries and regions with consumer law protections, users retain their rights under these protections. In Australia and New Zealand, consumers retain their rights under the applicable consumer protection laws and regulations.
Google:
If you are unhappy with Carbon for any reason, you are eligible for a full refund within the first 48 hours your first-time subscription. Please request a refund from our support team if you are eligible. All other refunds will be performed on a case-by-case basis and at our discretion.
Unfortunately, we don’t have the ability to issue partial or prorated refunds. You may be able to receive one at the discretion of Google by visiting https://support.google.com/googleplay/answer/7205930.
Important notes:
You will lose access to Carbon immediately when a refund is issued.
You can only receive a refund once, if you buy Carbon again you are ineligible for another one.