On an iOS devce (iPhone, iPad, etc):
Open Settings
Tap your name.
Select Subscriptions
Select the subscription you would like to cancel
Select Cancel Subscription at the bottom of the page
Select Confirm
On an OSX device (iMac, Macbook, etc):
Open the App Store app
Click your name or profile picture.
Select Account Settings
Next to Subscriptions, select Manage
Select the subscription you would like to cancel
Select Cancel Free Trial or Cancel Subscription
Finalize the cancellation by selecting Confirm
You can also use Apple's support portal to contact the Apple team directly regarding unrecognized or unwanted charges from their system.
Click here to learn how to use Rocket Money to cancel subscriptions billed through services other than Apple.