What have you identified as the purchases that have not been able to complete. They may be seen in red or listed as pending in your Purchase History.
View your purchase history for the App Store and other Apple media services - Apple Support
That is your first step to see what the charges are for. You may have to adjust the filter to list transactions beyond 30 days and make sure it is not restricted to only Paid purchases.
Purchases can only happen on your device when you have double clicked the side button on the Authorizations screen showing the amount, followed by verification with Face ID or Passcode. It cannot be done by accident.
- If you are a Family Organizer and use Purchase Sharing, that authorizes other members to make purchases on your account and will appear under their Apple Account, although with the Purchase History link, you can view their accounts as well.
- If you share your Apple Account with someone else, you have authorized them to make purchases on the account. Apple recommends to NEVER share your account with anyone else.
- If you signed up for a free trial and did not cancel a day before the subscription start date like the message said on the Authorization Screen requiring your double click, then you will receive the subscription charge. You can check your subscriptions here:
View or cancel app subscriptions on iPhone - Apple Support
You are correct, you will not be able to use the App Store while you owe money. Apple is not charging you for no reason, as it requires authorization as explained earlier.
