Hello,
More than likely, you will need to check your subscriptions in the App Store, in order to find out for what you are actually being charged, and it also may involve getting in touch with Apple Support, due to the credits Apple seems to be giving to you? You may be able to figure it all out just by taking a look at your subscriptions and how much you are paying for them.
Here are some further instructions, which I attained from the App Store help section.
Manage your subscriptions in the App Store on Mac
You can view or change options for subscriptions you purchased in the App Store, the Apple TV app, the iTunes Store, or Apple News.
- In the App Store on your Mac, click your name in the bottom-left corner, or click Sign In if you’re not already.
- Make sure you sign in with the same Apple ID you used to purchase your subscriptions.
- Click View Information, sign in again if necessary, then click Manage (to the right of Subscriptions in the Manage section).
- Click Edit (if you have more than one subscription), then do any of the following:
- Change subscription options: In the Options list, select a setting, then click Done.
- Cancel your subscription: Click Cancel Subscription, confirm the cancellation, then click Done.
Good Luck!