The "Federal No-Call List" only “protects a number for 5 years,” and then one must register all over again. Still, some know how to infiltrate it! Also, If you ever post an ad to sell something on Craig’s list, do NOT post your phone number either! I learned this the hard way.
Even some companies that many people would have considered otherwise reputable have been known to sell off people's information and it's even possible that the phone provider themselves could do this, when you sign up to anything, always look for a box to tick that states you don't want them sharing your details with other "select" companies and only give your phone number out if you absolutely have to. Once your information is given to "select" companies, they could then sell your information on again and again, until they're far from select.
Even if you never give your phone number out, sometimes the previous owner of the number has done, I've had numerous calls for the previous owner even many years on, all marketing calls or scams, I can tell them it's the wrong number til I'm blue in the face and they still won't stop calling, sometimes I've even told them it's a wrong number and they've still gone on and said that maybe I'd be interested in their special offer then lol!
I've had so many scam calls too including various calls that pretend to be from Microsoft Support, well it's laughable because they usually say they're from "Microsoft operating system" and their English is normally very poor, they claim they've detected errors on your PC that of course they're happy to resolve for you for "free" out of the kindness of their heart lol. Once I called their bluff to see what they were really up to and they tried to get me to give them full remote control of my PC, obviously I didn't give it to them and I suspect they were trying to steal private information like banking details, it's crazy that people actually fall for this, but obviously the occasional person really must do or they wouldn't keep trying it and I've had the occasional call from different numbers for years. Once a few years ago I looked up one of the numbers and found it had come from Jamaica, I even actually reported it to the
The Jamaica Constabulary Force (their police), but it's no surprise that they didn't bother to get back to me, I suspect they'd see this as low priority over there even though these scammers are committing very serious fraud and can make a lot of money from it.
Even recently I've had a fake call that claimed to be from Virgin Media (my ISP and phone provider) telling me that I've being offered something very special as a loyal customer, but what was worst is they knew my name and I confirmed later that it most definitely wasn't Virgin Media from other complaints on their official forums, but even when I told the women I knew it was a scam she still didn't give up and eventually I had to just hang up.
I've also apparently "won" prizes in various competitions, but if you've never entered you most definitely haven't and sometimes even if you enter something they call everyone saying they've won, once I did what was meant to be a market research survey in the street when everyone was entered into a prize draw and I apparently won the big prize holiday, but a friend also won and I found out that they were calling absolutely everyone. Of course I was very sceptical from the start and if you carefully read the small print you would find that the holiday wasn't actually free and the expenses you had to pay for would have cost more than the normal price of the holiday anyway, so it was a total scam, but a naff company like this has most probably still sold my information to numerous other dodgy companies making the cold calls even worse.
There's been numerous market research surveys too that are really only trying to sell you something, but they will all swear it's not a sales call until they try to hard sell you something later.
I had someone cold call only yesterday telling me about an incredible investment opportunity and again I had to hang up as they wouldn't give up no matter how many times I said I'm not interested and again they knew my name, it's another number now added to my block list. No reputable company you don't know would cold call you like this.
There's even times when a computer system will randomly dial random numbers until it rings and they get an answer, so it's impossible to prevent unwanted calls completely unless you block all numbers you don't know including withheld numbers.