While we do not know the specifics of the subpoena that your bank received, it is likely that the subpoena requires the bank to produce any relevant documents in its possession or control, regardless of whether the bank has retained the documents beyond any required retention period. If the subpoena requests documents that are not in your possession or control, and any required retention period has passed, you should note that in your response. If you do have the documents, you should produce them, even if any required retention period has passed.