I addition to my previous post, the Telstra website about spam/phishing calls says:
Calls imitating “support desk” staff looking to access your computer by pretending to know your “CLSID”. This is a non-unique identifier that scammers try to trick you into thinking is something only a legitimate support person would know.

A man with a strong accent - middle eastern perhaps, told me he was calling from Telstra and that someone was stealing my bandwidth, which is true - my internet data went up the other day between 6 and 7am when I was still asleep.
He asked me to go into command prompt to look up a number which he then read out to me for me to get confirmation that he was really calling from Telstra. He told me to go f*ck myself when I refused to verify if the number he said was the same as what I could see. All very strange and unsettling.