Requesting a refund for Cardiogram Premium
If you subscribed to Cardiogram Premium by mistake and require a refund, you'll need to submit the request through Apple or Google. Cardiogram cannot issue you a refund directly.
Follow these steps on your iPhone: https://support.apple.com/en-us/HT204084
Follow these steps: https://support.google.com/googleplay/answer/7205930