Managing an account: Checking or savings account

I opened a new checking account with Citibank and deposited my personal funds into the account. Shortly after opening the account, Citibank placed a restriction on my account and froze access to all of my money. I was informed that another bank was reporting a negative balance through Early Warning Services and that there was an attempt to collect the alleged debt. Citibank has not provided me with the name of the reporting bank, the amount allegedly owed, or a clear explanation of why my funds are restricted. I have not authorized Citibank to use my funds to pay any debt owed to another financial institution. My understanding is that the account is being restricted based only on a banking history report, and I am concerned about whether my funds are being held legally. I am requesting a written explanation of the reason for the restriction, the identity of the institution reporting the information, the amount being claimed, and confirmation of whether my funds will be returned to me or transferred to another party. I also request that Citibank provide the legal basis for continuing to restrict my access to my own funds.