called twice will not leave any message on answering machine

Caution. This sounded like the old virus and access to PC call. 'Jenny' called stating she was from Telstra Tech Department. I am fairly sure Telstra do not do this so I told her I do not have a Telstra account and that I think it is a scam, she hung up. It was the second call today

I called the number and no surprises that it could not be connected.

calls at any time nil message does not go to message bank.