485 finger print question

Dear all: I sent out I485 application last month. and got the notice letter last week. it said " If this receipt is for an an 1-485 application, please call the customer service at 18003755283 to make an appointment for fingerprint. therefore, I called this Monday and scheduled on Oct.25. but I got a letter today to ask me get the finger print on Sep. 20. I am confused with this. does anyone have this happen before? should I call again to cancel the appointment in Oct.
thanks for your suggestion