In NY we can us *72 each time the caller calls and when they make an attempt to call us again their call will not go through. But if you don't know who they are, you may be blocking someone that you want to hear from. It's best to try and find out who is calling you first. I strongly suggest and/or recommend that you seek Caller ID and Verification telephone services with your local telephone provider, making your LAN-line number private so that anytime a caller calls you that has a blocked or private number they will have to reveal their number by using *82 in order to speak to you and/or the call to go through to your residence. I have this feature and it's awesome.