Sup Anonerinos

Imagine you were owner of a business and you found out that someone was using your business accounts to buy good at inflated prices from a fake company the employee set up himself.

You find out the bank account and have proof of at least one such instance. But you would want to find out how long the fraud dates back, and how much money you were defrauded of. You have the bank account number but no clear way to gain info of transactions on that account.

Bar going to the police, is there any shady way to attain such information? I already searched for prominent leaks but could not find any of the bank the account is registered at.