Caller ID says "EXEL".  They leave no message.

I call back after hours (using *67 to block my number).  I hear the following, "Press 9 to be put on the do-not-call list." (I never do this as it can actually make things worse.)

So a spoofed caller ID and the failure to identify themselves.  Smells like a SCAM.

Just got a robe call from 484 223-3325 stating my IRS case could be escalating to collection status. I have no IRS case and they always send written notification. These people are scum and need to be stopped

If you know you don't owe taxes or have no reason to believe that you do, report the incident to the Treasury Inspector General for Tax Administration (TIGTA) at 1.800.366.4484 or at www.tigta.gov. You can file a complaint using the FTC Complaint Assistant; choose “Other” and then “Imposter Scams.”Jul 7, 2016

same as above caller "Just got a robe call from 484 223-3325 stating my IRS case could be escalating to collection status."
Hung up and blocked. All you can do.

Hung up before I could answer.  Just another scammer.