Definitely United Health. Unfortunately, if you call back as I did (from another phone), you'd better have your "8 digit number" handy to find out why they called. The automaton will cycle endlessly, asking for it, insisting on it, saying it doesn't match (even if you only scream "I want to talk to a human!"), and will NOT eventually route you to an operator as most systems do.
I got a slow switchboard connection as I spoke a greeting, and then a split second of a person's voice before I got the ascending "boo bee bee!" call cannot be completed as dialed noise. Then call was lost. Wonderful! In the middle of a workday too!