There is nothing you can do except stay alert. Simply apply the rule to any call that if a stranger stopped you in the street and started saying the same thing to you would you respond? If you get one of these calls, as suggested just hang up.
You can't block the calls but personally I only answer calls that show a caller ID and I can identify them. Calls from any unknown number are generally never going to be good (Scammers, Surveys, Politicians, Charities, Wrong Numbers, Tax Department). ANyone that actually has to get in touch with you will be able to write to an address.
So simple solution is if you don't recognise the number, don't answer.
They are annoying Indian call centres, who claim to be from Telstra, Tax Office (with threats), Microsoft, etc. They get past your registration with the "Aus. do not call" register" as they ring from overseas. Say "Namaste" or "E po" (rude) and hang up!