rings no messasge  no name  nothing

I don't know who these people are and they won't leave a voice mail. Since I don't know the number and it doesn't give a name of who it is. I won't answer it at all. I did answer a call from a number I didn't know and had to call my credit card company. They some how knew my card number and charged on it. Luckily I got the charge taken off. So don't answer a number you don't know. This didn't start until I bought my new iPhone and I got a new number.

I received a call from this number and no message was left.
I very rarely answer a call from a number that I do not recognize

I have been receiving calls from this number for days now.  They do not leave a message.  My phone is telling me that it is a call center.  I decided to answer this time.  It is a recorded message about signing up for health insurance.  They will transfer you to live customer support who will try selling you the insurance over the phone for a $25 fee.  I did not trust anyone who could not provide anything in writing.