They don't leave messages. I answer the call a couple of times and no one speaks on the other end. I call back. It ask me to speak to someone or be placed on the Do Not Call list. I've tried the Do Not Call list and they keep calling me back. I tried to speak to someone and it tells me that the person's mailbox is full and that you can't get a hold of them. Then this weird little creepy voices tells me goodbye. Them calling is annoying.

Rarely does requesting to be placed on numbers' "do not call lists" work. If anything, it brings more calls. What you're basically doing by telling them is confirming your number is open. Just leave it alone. Consider a call blocking device for a landline or look for a good call blocking app on cells.