Scam

If you call the number back, it will let you put your number on a do not call list.

This is probably a scam. I have my phone placed on a "Do Not Call" list so only certain people can call my phone...no idea who this is.

Placing your number on the Do Not Call list does not prevent anyone who dials your number from causing your phone to ring. What it does do is eliminate sales calls from law abiding telemarketers who screen numbers using the list to avoid making unwanted sales calls. Exempt callers such as charities, opinion polls, political callers and debt collectors are not required to screen before calling.  If you really want only certain people to call your phone you need to set up a "white list" using an external device for landline phones or a app for smartphones. The DNC lists will not accomplish that.

You think?! That's how you just let them know yours is an active number so they can sell the list to the next scam artist. You really have to be more vigilant, and suspicions these days. Unless you actually want more annoying calls.