Cash App is not a product or service of Apple. You would need to contact the support team at Cash App if that is the account you’re having issues with.
If you meant Apple Cash, you can see a list of transactions by going to your Apple Cash card in your Wallet app on your iPhone. If you have billing questions, you should see the merchant listed under transactions. If you still don’t recognize the charge/transaction call support at Green Dot Bank for additional assistance. Green Dot Bank issues and services Apple Cash accounts.
Contact Green Dot Bank by calling (877) 233-8552
If you charge is for an Apple product or service, post a reply here and we can see about a refund. Green Dot is probably your next step.