Fake calls from Comcast

I just got a call supposedly from Comcast that I had a firewall breach and that someone named [Edited: Personal information] had breached it and someone else that they could only identify as an iphone user had breached the firewall since 2/14/95.

The guy knew my name and I have the comcast number saved in my phone, so since that's what it said on my caller ID,  I thought it was  legit, but then he told me to go to my modem. As soon as I got near it, he hung up.  Totally weird and but I thought he'll call back.  while I waited (he never called back) I checked my firewall and it was fine.  Then I thought that maybe it was some sort of scam so I went online and found a chat that other people were experiencing the same thing.  I called comcast and asked about it. they said my firewall was fine.

I told them that someone is spoofing their number and doing this, and that it was concerning, but I was assured that the higher ups would be told about it. (I'm not holding my breath)