Got call. Didn't answer. No message.
Called number back. Which I rarely do.
Said can't be dialed.

I did not answer and they did not leave a message. I've blocked the number.

They called before, don't know who they are, I block all numbers I don't know, it is getting crazy with those calls.

Call came in this morning and I turned the phone on then off, then added the area code to my blocked number list.
My phone only allows me to block 250 individual numbers and I was at 235...
So I went thru then numbers in the blocked list and added all the area codes to the list that blocks all numbers starting with the number sequence added. This freed up 150 in the individual list which I now use for all the local area codes only.
Of all the area codes added for blocking I don't remember ever getting a legit call from anyone I know, so I have no problems blocking all numbers in those area codes.

Someone called from this number twice today.  When I answered, they hung up.