I agree with CTek. I also have a Panasonic KG *.* phone which is a slightler older model but allows 250 call blocks. (I am jealous of his/her model because they can block an entire area code.) The process is simple. When one of the blocked calls tries, our phone rings one time. I wish it wouldn't ring at all, but take satisfaction in knowing they can't get through to us. It has become a game in our house. The DoNotCall list is a national joke. It simply doesn't work. Our answering machine message states that if you appear as UNAVAILABLE OR PRIVATE CALLER or UNKNOWN CALLER we will not answer the phone. If you are a friend or someone we do business with, then please leave a message. In plain English, if we don't know who you are, and you need to keep it a secret, we Do Not Answer.
Telemarketers have found ways around the DNCL. Lots and lots of 'disposable' cell phones that can't be traced, calls that are routed through another country and calls actually coming from another country. They are relentless. I believe there is a great market for more and more sophisticated home answering devices created by these very annoying and unconscionable telemarketers. I have some great ideas for developers of such devices. One would be the ability to press a forward button on your handset (if you know darned well you don't know a soul in, let's say, Tuscaloosa AL, you hit the forward button and their call goes to another number you have selected from other callers you have already blocked. In other words, flip the telemarketer call to another telemarketer. Same idea as getting several junk mail 'offers', taking the response for one (making sure you've torn away your name or other identifying information, and stuff it into a different junk mail envelope as a 'response'. Let them pay the postage for more junk.
I'm not sure which panasonic model you have. I have the kx-tg41 series. It will block up to 250 numbers, and you can choose to hear the first ring or not. If your phone is like mine and you do not want the first ring, hit "MENU", then "#173", then choose "off". It works great. I prefer to have it ring once and these calls have turned from an annoyance to almost a game as I drop what I am doing to rush to the phone to block the call. I love this phone.
I've been on the do-not-call registry for about 5 years, but about 3 years ago, I started getting calls from "credit card services". They call almost every day, sometimes more than once. The real problem is that they frequently change their number. I strongly suspect that they are based "off shore", and the numbers aren't even correct, but "spoofed". I finally got a smart phone so I could block their calls. There are 2 free apps called Who Are You and YouMail that word together to identify spam and block calls in different ways. Every time they change their number, I have to add it to the blocked list, but after the first time, my phone doesn't even ring when they call. The real irony is that I freed myself of all credit cards about 15 years ago!