It sounds like you changed your forum account preferences and now they have changed back, and you have an unauthorized purchase on your iTunes Store account and have concerns about your account security. I recommend first changing your Apple ID password with this article:
Apple ID: Changing your password
- Go to My Apple ID (appleid.apple.com).
- Click “Manage your Apple ID” and sign in.
- If you have two-step verification turned on, you'll be asked to send a verification code to the trusted device associated with your Apple ID. If you're unable to receive messages at your trusted device, follow the guidelines for what to do if you can't sign in with two-step verification.
- Click "Password and Security".
- In the "Choose a new password" section, click Change Password.
- Enter your old password, then enter a new password and confirm the new password. Click Save when done.
The next time you use an Apple feature or service that uses Apple ID, you'll be asked to sign in with your new Apple ID password
You should also report an issue with the purchase to the iTunes Store support directly with the following article:
How to report an issue with your iTunes Store, App Store, Mac App Store, or iBooks Store purchase
To enhance security for your account you may want to look into Two-Step Verification to help prevent unauthorized access to your account:
Apple ID: Frequently asked questions about two-step verification for Apple ID
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