My Apple Pay account

Open the Wallet App, select the Apple Cash card, it will tell you what the transactions are for.

If you suspect a fraudulent transaction, you’ll need to contact Apple directly. Start with the Contact Support button at upper-right of this page.

If you think your Apple ID has been compromised, stolen, or hacked (Apple article):

https://support.apple.com/en-us/HT204145

You are not addressing Apple here. This is a user to user support forum and Apple does not participate here. No one here has access to any of your account info, and would not have any idea why your account shows -600. You need to contact Apple Support for help.

We can’t help you if you don’t tell us in detail what’s wrong.

Writing effective ASC questions (by Community contributor John Galt)

https://discussions.apple.com/docs/DOC-5931