Dear ___________ (name)
When I received your letter of ___________ (date) with my check attached marked “insufficient funds”, I called my bank immediately.
The gentleman I spoke with, _____________ (name) discovered that the bank had failed to credit my account with a substantial deposit I had made several days prior.
The bank has assured me that they will be sending you a formal letter of apology for their error. Attached is my check in the amount of _____________ (amount)to replace the dishonored one you have returned.