i noticed that they had called when I was gone from the house (they called a residence land line) - the caller left no message. Caller ID recorded was "CELLULAR CALL".
Based on other comments here, I did not call the number back & blocked it.
I don't answer call's from numbers I don't recognize - and didn't answer either call today when they called twice. And they called yesterday too... I've received numerous calls from this number and have the number blocked, but my Panasonic phone lets it ring once and logs that the date and time the number called.
They use magicjack connection. They can be purchased with fake ids and info. Report them as spam through TrueCaller. And they will not be able to call you back.