Bought new phones, paid in full, showing as EIP

I setup a new account today and paid in full for 4 new phones under a promotion through Costco. I'm not sure why, but somehow one of the phones is showing up as EIP even though I paid for it in full (I have receipts). How can I resolve this? Is this a T-Mobile problem or a Costco problem? I signed up because of a promotion and don't want to mess things up.