You can subscribe to Apple services like Apple Music as well as in-app services from various third-parties. You can see all of your reoccurring subscriptions in either iTunes on your Mac or in Settings on your iPhone or iPad. From there you can change the subscriptions to other plans offered, or cancel them. In many cases you can cancel a subscription but still use it until the next renewal date.
Well, you can do it from either your Mac or from your iOS device. So on your Mac go to iTunes and in iTunes you would go to Account and then View My Account. It's going to ask you to login. So once you're logged in scroll down the page and you'll see all your account information, purchase history, things like that.
If you have any subscriptions under Settings you're going to see Subscriptions and a Manage button. Click the Manage button. Now you'll see a list of your subscriptions. So you'll see Apple subscriptions mixed in with third party app subscriptions. So here I've got Apple Music. I've got iTunes Match and I have a MLB.com subscription that I use in their At Bat app.
So to look at any of them you simply click the Edit button. In this case with Apple Music I can see that I've got a subscription. I can see the other options for changing my subscription and I can see a cancel subscription button as well. I can even see my renewal date there and some other information, like for instance how long I can continue to access this subscription even if I were to cancel it right now. In a lot of cases you can cancel a subscription and then continue to access to say the end of the month or something like that. It depends on the specific details of the subscription. I can make changes or not. I can just hit the Done button after viewing without making any changes just to get out of the screen.
In iOS it's a similar process. You go into the Settings app. Now in the Settings app at the top now you've got your identification. So your Apple ID. You select that to go into Apple ID settings. Once you're in there you want to click on where it says iTunes & App Store. That will take you down into a screen that shows you some basic information. At the top where it shows your Apple ID it will be shown kind of blue so know you can click on it. So you want to click in here and that will then take you to a quick screen that asks what you want to do. You want to View your Apple ID. That in turn will take you down into your account settings.
Now in your Account Settings you will notice near the bottom you've got Subscriptions. Go into there and it shows you your subscriptions. So here's all the different subscriptions. If I click on the Apple Music Membership it takes me in there and it shows me similar options to what I saw on the Mac. So I can change my subscription. I can hit the Cancel subscription button and I can see information about the renewal dates and such for that subscription.
Now if you want more information Apple has a webpage for you on this. In here it walks you through many of the same steps, has a few more details, and even has instructions on how to change subscriptions from your Apple TV.
See Also: https://support.apple.com/en-us/HT202039