Update: They called again today and I talked to a person. I wouldn't give any of my info, but she was very nice and said that UHC should be very aware of them because they explore claims on behalf of UHC. So I called UHC again (third time in two days), and this time the rep checked with her manager and said that yes this is a legit call. UHC can't see the claim yet (I had an ER visit in the past couple of weeks), but Optum (not to be confused with OptumRX) is a company that calls about accident claims to see if it qualifies for worker's comp. I told the UHC rep that Optum's role and mode of calling needs to be made clear to other UHC reps so that people can confirm that this is not a scam. Anyway, because I wouldn't give info to the Optum rep, she agreed to send me a questionnaire in the mail that I could verify with UHC. I did not give her my address, just asked her to use the one they had on file.