I have already canceled my subscription, and I would like to request a refund for the recent charge on my LingQ account."
You are subscribed to LingQ Premium membership via the iOS app and the Apple Store. To cancel your subscription, please log in to your Apple Store account and cancel it there.
Here’s how you can do that: If you want to cancel a subscription from Apple - Apple Support
You can request a refund from Apple here: http://reportaproblem.apple.com/ Unfortunately, they don’t allow us to issue a refund on their behalf.