AllianceOne Receivable Collections on an unknown account at the Post Office (during time I was living outside of the USA) Gig Harbor , Washington

I just checked all 3 of my credit reports, which I do every couple of years to make sure everything is current and accurate.  While checking my credit report a few days ago, I discovered that I had a negative report on my record from AllianceOne Receivable in Gig Harbor, WA for an unknown amount, unknown account, unknown unpaid bill at the Post Office.  Although this amount has been settled (by someone), I have no knowledge of this whatsoever.  The problem is that it has now shown up on all three of my credit reports impacting my credit score and ability to obtain credit at favorable rates.

The second issue...  The account indicated at the Post Office for which was supposedly overdue could not have been me.  I had been living overseas at the time this incident was reported.   

I have enquired with AllianceOne Receivable via the phone and so far they are unwilling to remove this from my credit report.  I have also filed disputes with each of the credit reporting agencies.  So far nothing has been favorable.