As Luke has suggested, if people simply did not answer these random, unknown calls, or refused to call the number back, especially when no message is left, then they would eventually stop.
I guess not everyone has caller ID on their phone, or are concerned about missing something that they answer the call. The result is the perpetrators know they will connect with some, possibly gullible folk who may be successfully scammed.

Caller: My Charity Survey

After they told me who they are I said no thanks and hung up.

I cannot comprehend that this is considered business practices. These calls come in all the time from various similar numbers. I never answer but look them up. Alway charity’s, electricity, health insurance. What a dumb way to run a business

As I don’t know the number didn’t answer. Now blocked.

Another and another and so on from same format number and no messages. Just keep blocking them.

Sick of these calls - does the 'Do Not Call' register even mean anything anymore?

Had a missed call from this number. I have no connection with anyone or a business in QLD, so I decided to check this site before returning the call. I'm glad I did. Charity Survey calls every week at least from different numbers. Really thankful for this website. People can compare "notes" :)

These lowlife pests are certainly persistent. I've had at least five calls now from similar numbers, have never answered, but the disgraceful harassment continues.
I picked up the phone today to shut it up, not to speak, and the person on the other end, if there was one, didn't even bother to speak (as usual with these scam calls from scumsuckers).
My (perfectly good) phone stores only a limited number of blocked senders so I have to unblock one in order to block the next one. When the scammers use multiple numbers I can't block them all and it drives me crazy.
Please don't answer calls from unknown numbers, ever, or the scams and harassment will never stop.

No message left. Another scam/spam call.

Also rings on 07-5346440. Caller Hangs up if answer machine cuts in, with no message.

Area ID shows up as Caloundra QLD scam

Caller: Peter

Aussie speaking male asking if I would answer some questions for a charitie survey - I declined

Didn't respond to greeting

no message left nuisance call !!