If you wish a refund: 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. You can always ask, and people do get refunds on a case by case basis, but Apple can also say no. To request a refund:
Request a refund for an App Store or iTunes Store purchase - https://support.apple.com/HT204084
To request a refund or: Report a Problem - http://reportaproblem.apple.com - "Sign In for help with iTunes purchases made in the last 90 days" (Does not work for subscriptions, use the contacts below.)
If a reporting a problem request is unsuccessful you can also try:
Other ways to contact iTunes Store Support:
https://www.apple.com/emea/support/itunes/contact.html
https://support.apple.com/country-selector/itunes
Read use details for "free" apps. Many have in-app purchases and/or free trials which automatically turn into paid subscriptions after the trial ends.