Caller was from overseas and claimed to be calling from Telstra.
Apparently my NBN speed was fluctuating and he wanted to help me fix. When I asked for confirmation he was from Telstra and I demanded to know my telstra account number or amount of my latest bill from Telstra. If the caller could provide this information, then the caller would appear genuine. However the caller could not provide me with the information I asked for so I suspect the caller was not from telstra.
So I hung up on the caller. . Appeared to be scammers.