Citibank Bank Account Or Service Complaint

Citibank Bank account or service department,

Checking account Deposits and withdrawals District of Columbia

My bank sent an online payment to one of my creditors. The creditor said they never received the check. The check was cashed and endorsed but the endorsement was not one that the creditor uses. We sent an Affidavit of Forgery, Alteration, Counterfeit or Unauthorized remotely created Check to the creditor so that our bank could open a Fraud Inspection investigation. The creditor would not sign it because they say they never received the bank. Our bank can not open the investigation without the affidavit. We been going back between the creditor and our bank for over a year. The creditor and continuously refused to sign it.