If you have no recollection of having an account with them, you can make the statement that it is not an account ever authorized by you. That is not a knowingly false statement, and thus carries no penalty for its assertion. You can thus file a police report, stating that its presence in your CR would necessarily have resulted from use of your identity without your knowledge or consent. That police report opens up doors for you under the FCRA. Such a report, under the provisions of FCRA 603(q), is called an "identity theft report."
Armed with an identity theft report, you can use that under several sections of the FCRA, such as section 605A to block inclusion in your CR, and as documentation for a dispute under section 623(a)(8) sent to the credtior of your assertion of "account not mine." The new direct dispute process, for example, specifically identifies an identity theft report as supporting documentation for a dispute of credit reporting. That makes it more than a bald assertion, but rather an assertion attested to by way of statement to a law enforcement agency. See 16 CFR 660.4(d)(3), which is part of the implementing regulations governing the direct dispute process.
File a police report, and dispute as "account not mine," including that as documentary support. That will at least prevent your dispute from being held "frivolous or irrelevant" for failure to provide supporting documentation. Then they will be required to investigate, and report their results back to you within approx. 30- days.
.... by the way, what was the "negative hit" they reported? A 30-day late? That might stand as separate grounds for a dispute on the grounds that they never sent you a billing statement with a due date upon which to base any holding of delinquency in payment. That would require their production of a billing statement to support any results of investigation of your dispute asserting that you were billed, and delinquent on that statement. Another course to consider....
