Caller: Claimed to be from Australian Cyber Security

Called me on a phone number not associated with my email account and advised I had been attacked and both my email address and IP address had been changed to appear to be coming out of California and being used for several illegal activities. The man had an Indian accent, kept refering to me as a Australian Ciziten and bypassed answering my question as to why he was calling me from a mobile number.
I have confirmed there is a government department called Australian Cyber Security Commission and requested information on whether they contact Australian Citizen's directly, through phone numbers not associated with "hacked" email addresses to advise people they have been under attack. All the information the caller had is associated with my Optus account but not the provider of my email account (two different providers) so I feel this is just a flow on from Optus being hacked and my information now being out in cyber space etc.