I had a subscription that I thought I could cancel and get my money back?

You must first cancel any subscription automatic renewal (if you simply delete an app this does not cancel subscriptions):

View, change, or cancel your subscriptions - https://support.apple.com/HT202039 - "Your membership or subscription might renew if you don't cancel your membership or subscription more than 24 hours before your renewal date." At this stage the renewal is considered a purchase. For a new subscription the sale is probably effective from when you first agree to subscribe.

Review:

Report A Problem to "Sign In for help with iTunes purchases made in the last 90 days" or ask for a refund. Click on this link --> http://reportaproblem.apple.com

For subscriptions, "The Report a Problem website shows most subscriptions, except those for Apple services and iCloud storage charges." [https://support.apple.com/HT201382].

If Report A Problem does not work for a subscription refund you may have to make a special request using one of the contact links below.

Contact iTunes Support:

https://www.apple.com/emea/support/itunes/contact.html

https://support.apple.com/country-selector/itunes

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.