Angie, when the OC has changed their balance to $0 its generally because they have SOLD the debt to a JDB (junk debt buyer) or CA.
When the OC still owns the debt and they have a CA collecting then both accounts will show the balance. From what I have seen on my own reports and heard from others when the debt is actually sold then the OC will change it to $0.
I would write a letter to the OC to verify whether they have the debt any longer.