Let your boss know about this SCAM. You are not warned if a summons is coming and they must (by law) stop calling you at work if you request that. Repeated calls are a violation of the FDCAP (and tells you loads about the caller).
I got a call from this number to my employer and to family members saying that they were from ACS and left a case number. When this number shows up on my phone is says "SCAM LIKELY." How do we report them?