Telstra does want to know, it's just that the attempted scammer sent an email so Telstra wants you to report the incident on-line using
REPORT MISUSE OF SERVICE
and you could also try the acma
Online enquiries | ACMA -- the .gov.au is a fairly good assurance that the acma's website is sort of OK.
Note that I haven't done much more click on a few links on the ACMA's web site to get to the linked page
also note
Although Telstra's call centre may no longer be located off shore -- something I don't really know for sure -- the call center "operators" will not be trained in how to respond to scam or phishing emails. That's why Telstra's web site gives a link to their "report misuse of service" on-line form