This number has been calling my cell phone several times a day for weeks. These are unwanted calls. They need to be stopped. When I call back, they won't answer their phone but ask you to leave your number. They tell other people they can opt out if they don't want them to call them. But they just keep calling. Again, these people need to be stopped.
Got a call on my cell phone a few minutes ago. They hung up before I could get to the phone and they didn't leave a message. From posts on other sites, this appears to be some kind of solicitation. Note that you should NEVER call an unknown number like this back. As soon as you do, you establish a relationship and they can ignore the DNC list.