Never answer a call from an unfamiliar number. If they don't leave a message, it's not legitimate. DO NOT ANSWER such numbers or call them back. That will tell them and their many spam partners that yours is a live, operating number and you'll get more and more calls. Block the number if you have that option.
I get calls from these morons too. They never leave a message and are always calling. I think this is a fake number. Like one from an app because when I trace it from my server it's not in this country. It's a fake VOIP number.