Received a call from this number, I didn't answer and no message was left when I checked it later.

This person keeps calling, at least 10 times a week, I don't know who it is but have reported it to trace. They say to press any number, then I'm disconnected.  If I call back the number it doesn't go anywhere or to anyone. If you also would like to do this when you get nusance callers, just press *57, wait for the message, and hang up.  The phone company will put a trace and file a complaint. However, these people do use many different numbers, and will most likely will continue calling until all numbers are blocked. The other thing you can do is block the calls, but first check to see if it is free.  Lastly, you can call the Operator and file a complaint that way.