Trying to undesrtand why I got denied reimbursement for switching to ATT from Sprint.

I submitted all the documents and I thought everything was correct.  I received a letter in the mail from ATT saying that my submission was denied because there was no ETF or EIP on the bill.  Upon looking at my final sprint bill, all I could find was a "Total Lease Amount Due" for the phones that I still owed on.  Wouldn't this be the same thing as the EIP (Equipment Installment Plan).  Nowhere on the bill was there an EIP or ETF so now upon switching to ATT I am stuck with a 500$ Sprint bill.  What a hassle.  Literally the exact thing happened to me when I switched from ATT to Sprint in the first place.  Any help would be greatly appreciated.