Cancel the monthly subscription

If the invoice has to do with an app that has a subscription associated with it, see -> Delete apps on your iPhone, iPad, and iPod touch -> Delete apps on your iPhone, iPad, and iPod touch - Apple Support

• If you delete an app, it doesn’t cancel in-app subscriptions that you might have. While deleting an app, you might see a Cancel Subscriptions option. Learn how to cancel your subscriptions.

If you don't want to continue a subscription you need always to cancel that subscription in time, see the following Apple articles:

If you want to cancel a subscription from Apple

If you want to cancel a subscription from Apple - Apple Support

If the subscription that you want to cancel is not listed

If the subscription that you want to cancel is not listed – Apple Support (UK)

Manage subscriptions on Apple TV

Manage subscriptions on Apple TV – Apple Support (UK)

• You can modify or cancel subscriptions available on Apple TV, including Apple Music, Apple TV channels, Apple Arcade or individual apps.

See also ->  Downgrade or cancel your iCloud+ plan

Downgrade or cancel your iCloud+ plan - Apple Support (PH)

If you have received an invoice from Apple, on every invoice from the Apple Store and/or iTunes Store always states what you have purchased (and/or concerns a subscription) and the amount.

Tap on Report a problem on the invoice.

Or try to ->  Request a refund for apps or content that you bought from Apple.

Request a refund for apps or content you've bought from Apple – Apple Support (UK)

If you have requested a refund, you must wait until Apple has approved. Then you will receive a message from Apple.

Refunds are not guaranteed. For more information, see the Terms & Conditions.

or see: 

If you see "apple.com/bill" on your billing statement

If you see "apple.com/bill" on your billing statement – Apple Support (UK)

Turn Renewal receipts -> OFF.