Confirming if a call is legitimate

I have been receiving vms from someone claiming to be Comcast Xfinity but the number doesn’t show up as verified  and it’s not on your official site— is there a way to confirm if it is legitimate? (I see no messages in my app or indications of an issue/that someone is trying to reach me).  Google says the issue they are reporting may be legitimate (noise coming from internal network) .. but the one time I was free to answer it sounded like a super sketchy call center. I tried asking the app assistant about it or for someone to contact about it a dozen different ways and got led in circles- I don’t want to sit on a phone wasting my time waiting for a rep either if it’s a scam.  (Why isn’t there a simple way to check?). I am not having any issues with my connection btw.