Purchase

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."

Hello Katy,

Read this document carefully. In particular the first part. Then follow the appropriate instructions.

https://support.apple.com/en-gb/ht201382