Check -> Go to -> Settings -> your name -> iCloud -> if you see 50 GB (or 200 GB or 2 TB) then you have an iCloud subscription.
If you have an iCloud subscription, you will receive a monthly bill from Apple, check your email box.
You pay monthly for iCloud storage.
See the following Apple articles:
View your purchase history for the App Store, iTunes Store, and other Apple media services
View your purchase history for the App Store, iTunes Store, and other Apple media services - Apple Support
How apps, content, and subscriptions from Apple are billed
How apps, content, and subscriptions from Apple are billed - Apple Support
If you see "apple.com/bill" on your billing statement
If you see "apple.com/bill" on your billing statement – Apple Support (UK)
If you see an unexpected charge:
You can request a refund* for a purchase that you don't recognize, but you must pay for the purchase first. You can also cancel a subscription if you don't want to continue it.
*You must request the refund within the refund period.
Refunds are not guaranteed. For more information, see the Terms & Conditions.
See also -> Identify legitimate emails from the App Store or iTunes Store
Identify legitimate emails from the App Store or iTunes Store - Apple Support