For past 2 weeks have been getting multiple calls from 03 9970 96XX but they never talk or leave a message. Unfortunately this scammer changes the last 2 digits on each call so blocking the number hasn't worked for me. I've blocked about a dozen variations so far but here's another i've just received.

Caller: Allways starts with 03 997096..

What do they achive by all the calling but never speaking??

I suggest blocking all calls from the range of numbers (03) 9970 96xx, if you can. They are being used by relentless scammers who have started calling constantly (the morons keep trying even though no one has ever answered and the numbers are in fact blocked).
Some reports suggest that this is a re-emergence of the "Kindness Project" fake charity scammers who did the same thing for a long time. It's now being called something like "Charity Prime".
Please do not answer calls from scammers, ever, or call them back.

Caller: Indian Scammer

Indian call centre called, hung up without speaking after a few seconds

Nasty Scam Call

Number called every day 6 times.never leaves message and scam for sure??

scammer

For what seems like the ten thousandth time - some pest phones but hangs up without saying anything.

No message left. Another scammer, another number blocked.