On your iPhone, iPad, or iPod touch

  1. On the Home screen, tap Settings.
  2. Tap iTunes & App Store.
  3. Tap your Apple ID
  4. Tap View Apple ID. You might need to sign in.
     
  5. Under Subscriptions, tap Manage.
  6. If you don't see a subscription in iTunes and are still being charged, make sure that you're signed in with the correct Apple ID. 
  7. Tap the subscription that you want to manage.
  8. Use the options to manage your subscription. You can choose a different subscription period, or turn off Automatic Renewal.
  9. Turn off Automatic Renewal to cancel a subscription. Your subscription will stop at the end of the current billing cycle.


On your Mac or PC

Click to open iTunes and sign in to your Account Information, or use the steps below:

  1. Open iTunes.
  2. Click Sign In and enter your Apple ID.
  3. Click your name, and select Account Info from the drop-down menu
  4. Enter your password again.

On the Account Information screen:

  1. Scroll to the Settings section. 
  2. To the right of Subscriptions, click Manage.
  3. If you don't see a subscription in iTunes and are still being charged, make sure that you're signed in with the correct Apple ID. 
  4. Choose the subscription you want to manage.
  5. Use the options to manage your subscription. You can choose a different subscription period, or turn off Automatic Renewal.
  6. Turn off Automatic Renewal to cancel a subscription. Your subscription will stop at the end of the current billing cycle.


More info at https://support.apple.com/en-us/HT202039