From what I can tell the app itself is free, but not unusually there are in-app purchases to actually do much with it. You have to cancel the subscription, not the app itself. Deleting the app will still result in a subscription charge.
View, change, or cancel your subscriptions - https://support.apple.com/HT202039 - "Learn how to view your subscriptions that renew automatically, change your subscription period, and turn off Automatic Renewal." "If you don’t cancel more than 24 hours before your renewal date, your subscription might renew."
There is no guarantee you will receive a refund unless you are in a region where Apple is mandated to do so.
Apple's terms of purchase in the USA are, "All Transactions are final" (https://www.apple.com/legal/internet-services/itunes/us/terms.html), but some countries have different laws so check terms for your country at: http://www.apple.com/legal/internet-services/itunes/. If sales are final then it is Apple's decision if they want to grant a refund.
Get help with an item purchased from the iTunes Store, App Store, Mac App Store, or iBooks Store - https://support.apple.com/HT204084
If you see ‘itunes.com/bill‘ or an unfamiliar charge on your bank, credit card, or debit statement - https://support.apple.com/HT201382 - "Before you contact Apple to request a refund for a charge you don't recognize, follow the steps below.
Report a Problem - http://reportaproblem.apple.com - "Sign In for help with iTunes purchases made in the last 90 days"
Other ways to contact iTunes Store Support:
https://support.apple.com/contact
https://www.apple.com/emea/support/itunes/contact.html
People responding on this forum are only other users like yourself. Use the above methods to contact Apple.
