I got a "Security Alert" email saying that someone was filling out a tax return with my information on a different account. How do I verify it's not a phishing attempt?

It is possible that the email may be a phishing email; can you please report the email to https://security.intuit.com/ ?  Here are some ways to tell.    https://ttlc.intuit.com/replies/4256209

What should I do? Calling Turbo Tax support does not seem to wrk.

Sounds like it could be phishing.