Immediately go to www.AnnualCreditReport.com and get a FREE (not sighing up for any monitoring) credit report from at least one of the three major bureaus: Experian, Equifax, and/or Transunion.
You’ll get it instantly after answering some questions that only you can answer. Then look for an account from that lender. Maybe someone opened new credit in your name. (All three bureaus should have the same info, but in this case I would get a report from each of them!) You get one free3 one from each bureau every year — and this is the time to use that privilege. At the same time, put a freeze on each credit report so that if there IS fraud, they don’t open any more accounts!
Either way, immediately contact the company that billed you and say you have no idea how that was billed to you. You’ll have better ground to stand on if you can tell them the account isn’t even on your credit report.
And your final step may be to file a police report about identity theft if the company that sent the bill won’t fix their error. Keep careful records of whom you spoke to.