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You can always make an informal request for recon, making your case, but you have apparently done that.
The FCRA dispute process is administrative, and does not include any formal appeal procedure.
After you have received a verification of accuracy of disputed information, you then acquire under FCRA 623(c) the right to file a civil action and get the matter before a court for full review, including discovery and consideration of all documentary evidence by both parties.
If you have completed a dispute through a CRA and still disagree, you now have the right to file your own civil action and get your position reviewed by the courts.