this number calls regularly, when I answer, there is a brief silence then the phone call is disconected

I think it's non-profit (charity) telemarketing.

This number calls then hangs up. Have tried calling back but silent when it answers.

selling something not wanted

It is Rate Detective - selling loans and insurance Received many calls before actually someone spoke to me

They are income insurance marketers
They try selling income insurance where they direct debit an anual fee from your super

It is rate detective.

phone calls driving me crazy from that number, i will not give to them now , they have made us very angry

After many many calls as above, I finally got a human voice on the other end. It's The Australian Childhood Foundation.

Exactly the same experience as above, numerous calls and hanging up after a few rings if I try to call. While I am on the DoNotCall Register (https://www.donotcall.gov.au), their rules include the following FAQ:
2. Will registering my number stop all telemarketing calls and marketing faxes?

No, registration won't stop all calls and faxes. Some public interest organisations (e.g. charities, political parties and educational institutions) can still call numbers listed on the register. This ensures these organisations can continue to provide valuable services to the community.

Rings then hangs up

Calls both landline and mobile then hangs up. When I try to call the number again hangs up

Have been receiving these phone calls.Ringing just to see what is the best time to get you!! This is the second one today .Just wish they would go away .

Totally agree. Received several calls. Hiw has time for this stuff

received 2 calls per day to both landline and mobile - caller unkown, now blocked!!!