First, it is perfectly proper for both the OC and the debt collector to report a balance.
When the OC reports a balance, it reflects that they still own the debt, and that the debt collector is only an assinged agent to collect on their behalf.
The balance reported by the debt collector under their CA reflects the amount of the remaining, outstanding debt they are authorized to collect upon.
Kinda apples and oranges, although they appear to be duplicative.
If the OC still owns the debt, then legally either the OC or the debt collector can accept payment. However, many OCs, once they assign collection, will, as a matter of practice, refuse to negotiate or accept payment, and will require that you deal with the debt collector. That is their option, and is what they are paying the debt collector to do.
If you pay either party, then both will therafter report a $0 balance, the OC $0 balance reflecting that the debt is satisfied, and the debt collector $0 balance reflecting that they no longer have a debt to collect upon.
As for the dates you make reference to, they are a bit confusing. If the "first delinquency," which is assumed to be your DOFD, occured in 12/2008, then that individual monthly delinquency would cease CR inclusion after 12/2015 (date of monthly delinquency plus 7 years) If the DOFD is 12/2008, then the CA could continue to be included in your CR until after 6/2016 (7 years plus 180-days from DOFD). That does not mean that the CRA cant or wont delete earlier, which makes use of an "expected deletion date" to back-calculate the DOFD a bit iffy.
The SOL is irrelevant to any credit reporting determinations.
