If you don't recognise the number, don't answer it. If it's important to you, s/he/they will leave a message. No message, it's not important. And never, ever return such calls. Why? By answering/returning such crap calls you have just confirmed that you are a live sucker. Your number will be sold to thousands of scammers. Be prepared to be swamped with b/s calls, b/c you have just set yourself up for a lot of grief. Learn about blocking. Get a Google Voice number - the app offers a lot of options, including transcript of messages and blocking. That's the number you want to give out to people whom you do not know, who are not close and trusted friends and family.