Called my cell and left no message. My approach - do not answer lest they confirm it's an active number. Answer and you get - a recording or silence or someone trying to sell you something. Do as you wish but I find trying to bother a professional scammer not to be my best use of time.
Didn't answer as I didn't recognize the number which has called my cell phone before. They left the usual message of winning a cruise. I don't think so! I finally took the time to block the number.