Please click this link via the device you use to play Peak to cancel your subscription:
https://apps.apple.com/account/subscriptions
If you can only see the "Resubscribe" option at the bottom and you are logged in with the correct Apple ID, this means that you have already cancelled your subscription successfully.
For additional information on how to cancel your subscription please have a look at this link: https://support.apple.com/en-gb/HT202039