How to block phone calls that show no ID

Many calls like the ones you are receiving are scams/phishing attempts. They are made by criminals that prey on the unwary. Note that the calls you are referring to, those showing no caller ID, are very difficult, if not impossible, to block.

But, there are things you can do to lessen the annoyance of such calls. For example, I hardly answer my land or iPhone any more. I only answer if caller ID or my contact list shows that I probably know the caller. Also, I figure that anyone that know me will leave a message if they have anything important to say and I don't answer. 

Your phone service provider may have a call blocking list on their web site that allows you to block calls from a given number.