I had a business account that had fraudulent activity. In person at a branch(early February) I sought to close the account and pay the negative balance. The Credit Union employees advised a new account be opened and the negative balance be transferred during investigation. I received little communication (1 call which I returned in April) about the progress, but having worked for the institution I was aware that the investigation could take some time, but a provisional credit would be issued. However, yesterday attempts to access personal accounts with the same institution were denied and the new account had been charged off and all personal accounts restricted. When I requested the name of the employee that placed the restriction on the account I was told that information was confidential
Credit unions are regulated by the NCUA (might be FDIC now). In any event contact the regulators to complain.
Any business litigation attorney with banking experience should be able to help you but there must be more to the story than you have disclosed in your question.