OK, this seems to be a common thing lately, I've been dealing with similar myself.
FCRA requires the credit bureaus to consider all evidence you provide. In my case, the CRA claimed that the evidence I provided could not be considered because it came from the original creditor and not the debt collector. I was finally able to get the CRA to admit that the OC's letter that I provided did indeed apply to the same account in question.
Rather than go back and forth endlessly, I believe your best bet once they refuse to consider your evidence would be to look into legal action. It seems like the only thing getting them off their back sides is the threat of having to pay out money for their actions.
They do like to split hairs...example, if you sent them a copy of a court judgment, the court judgment likely did not identify the specific account, or possibly even the original creditor. That would be spelled out in the complaint that Jefferson filed when they sued you.
You might consider contacting fingerhut directly---if it says "fingerhut" as the furnisher, then that's the fingerhut entry. It should say that it was sold to a debt collector like you indicated--fingerhut sells its debt accounts off regularly. But you need to tie that fingerhut entry on your report to the win in court. In order to do that, I would see if you could provide to fingerhut the following:
1--copy of your credit report entry from fingerhut--it should have a partial account number on it.
2--copy of complaint from Jefferson, which hopefully identifies something about the account so that it can be seen that it's the same account. The balance, dates, partial account #, and so on...they all fit together to identify the specific account.
3--the court's order stating that the addresses, etc, that they have on file for this account are not attached to you.
The goal would be to ID the specific account as much as you can, and then show them that a court even found that you were not connected to that account. From there, request that fingerhut remove its false reporting immediately. You might even treat this like an intent to sue letter, explaining to fingerhut that unless they pay attention to the fact that this is clearly not your account and remove it, you will sue them for damages under FCRA.
Alternatively, you might also look for a consumer law attorney and bring all of this to them. Usually, their initial consultation is free and many of them would probably take a case like yours on contingency basis.
