this guy mentioned that he call from Telstra and he is going to disconnect your internet service and want you to do as he say.

Caller: ‘Jack Smith’ from Telstra

First a suspicious silence, click and then a connection to a noisy call centre. This person said someone was using my internet for illegal purposes. He wanted me to open my computer and log in. I told him I didn’t trust it and that I was happy to speak to someone at Telstra if I could contact them myself. He tried to pursuade me to go on with the phone call and his ‘assistance’ and when I refused he said my internet would be disconnected. The person had a strong accent, very unlikely to be a ‘Jack Smith’ and there was a lot of background noice (call centre)