I have a theory about this, based on recent experience.

Try searching in Facebook messenger using the cellphone number of someone who is not in your Facebook friends list.  If they have associated their number with their messenger profile, you'll get a search hit with their name.

So, if you're a scammer with a list of (even random) numbers, you can plug these into Messenger, and get names to go with them.

I'd say Public Records like White Pages

DjShadow:

 

I'd say Public Records like White Pages

 

Certainly not in my case - my cellphone has never been listed in any directory

Domain whois records is another place people put personal details on

Many new cellphone apps demand/require access to your contacts list... i once rang up about a private car listed on TM and the caller answered "Hi Neil from Gxxxxx" (even knew where I used to live!) and when i queried how he had that information he said he "has an app" on his Android phone which tells him.

I think some less reputable chat apps might store all your contacts in the web and share them with other users. I know for example that Whats App searches out all the numbers in my iPhone contact list and adds them as potential message options... often with lots of information i don't have in my own contact list (full name, photo etc.)

It's quite possible that someone you know has installed one of these apps and has shared your information from their own list 8(

in these days, its no longer possible to 'protect' yourself... if somone you know shares your information (even unknowingly) once its out there... 

PhantomNVD:

 

Many new cellphone apps demand/require access to your contacts list... i once rang up about a private car listed on TM and the caller answered "Hi Neil from Gxxxxx" (even knew where I used to live!) and when i queried how he had that information he said he "has an app" on his Android phone which tells him.

 

 

 

Probably what I run. Was handy to find someone whos phone was used to maliciously call me by kids last week..

https://play.google.com/store/apps/details?id=com.truecaller&hl=en Trolls Linked in the web

Oblivian:

PhantomNVD:

Many new cellphone apps demand/require access to your contacts list... i once rang up about a private car listed on TM and the caller answered "Hi Neil from Gxxxxx" (even knew where I used to live!) and when i queried how he had that information he said he "has an app" on his Android phone which tells him.

 

Probably what I run. Was handy to find someone whos phone was used to maliciously call me by kids last week..

https://play.google.com/store/apps/details?id=com.truecaller&hl=en Trolls Linked in the web

Scammers trade lists of people's details. The more details on the list, the more money the list is worth, because it's more likely to result in a successful scam.

So a list of people's names is worth (say) $10, a list of working phone numbers is worth $10, whereas a list of people's names WITH phone numbers is worth $20, and a list of names WITH addresses and phone numbers is worth $30.

When a scammer gets a list of names, the first thing he does is to try to match up details from other lists he already has. The second thing he does is try to scam you. The third thing is to sell/trade the list to as many other scammers as he can, before anyone else can sell the same list around.

I'm guessing that some scammer has got your phone number. He's tried you, failed, and onsold it (along with a bunch of other numbers) to 2 other scammers, one of whom has matched it up with your name somehow. I guess you can expect more calls in the near future.

Do try to make life unpleasant for scammers who call you by wasting their time and mocking them and insulting them.

If you've ever registered a domain name, they sometimes use the publicly viewable name/number from these records. 

Electoral role is public information, has names and addresses

http://www.elections.org.nz/research-statistics/electoral-rolls-and-enrolment-data

Cross reference that with white pages information, job done.