unknown number calling but they didn't say anything when you answered

In one day got 9 calls from this number, no one leaves a message. I am so sick & tired when working shift work to be woke up by these a***oles calling. I tried call block & it did not work! Who the hell calls from this number??? I bet another dam scammer!!! Why else would they not leave a message!! How to stop stop them is unknown to me! I'm on the do not call list! That is another F**King joke!