Hi
If you are referring to a credit balance on your Apple Pay Cash Card, then I suggest that you contact Apple Support via the link at the bottom of this page:
If you need help sending or receiving money in Messages with Apple Pay - Apple Support
If you are instead referring to your Apple ID account (including iTunes Store and App Store), then if you do not believe that your account balance is correct, then follow the instructions here to check your purchase history, which may include, for example, subscription payments:
See your purchase history in the App Store or iTunes Store - Apple Support
If you still believe that the balance is wrong, then it may help to sign out of the iTunes Store and App Store on all of your devices and then to sign back in again.
If you still need help, then contact iTunes Support:
I'm afraid that no-one here can look into the issue for you. You are not talking to Apple here - this is a user-based technical support community.