Unlock phone request - upgrade error message- replacement refurbished phone

I am trying to unlock a phone that was paid off months ago.  My ATT account is closed and paid off (actually, I'm due a balance) over a month ago. 

When I try to use the unlock device webpage, I get a message saying that I recently upgraded and need to wait 14 days.  I initially got this message a few weeks ago when I tried to unlock, but since we had recently closed account, I thought I needed to wait.  It's now been over a month since the account was closed.  There has been NO activity on my account in the past month, but I am still getting the message that I need to wait 14 days due to a recent upgrade. 

Please advise with how I can unlock my phone, please.  I have paid my contract.  

UPDATE:  After doing some research, I think I know what the issue is, but still don't know how to resolve.  My original phone (Samsung S7) was insured, and when it stopped charging, I was given a new (refurbished) phone by the insurance company.  All of this was done through the AT&T insurance provider.  The refurbished phone I was given was a Samsung S8.  My installment plan for the phone was paid in June 2018, but it doesn't show that THIS phone was paid off, because this was the replacement phone I was sent by the insurance.  

PLEASE HELP!  I even went to the ATT store, and they gave me a  phone number to call.  That person "transferred" my call to someone else, and I was disconnected.  I would like to figure this out ASAP.