There is no need to be concerned if you receive unknown calls and do not recognize the caller. Here are a few tips you can follow.
First, try to google that number.
There is also a website called WhoCallMe that you can use to enter an unknown number.
Try spy Dialer, another free service, to find the unknown number.
Read more: https://getassist.net/find-who-this-phone-number-belong-to/