I called back number (08) 8547 4585 rang 5 times then goes to busy tone.

This is a scam. Someone called Daniel with an Indian accent has called three times in the last week, claiming he was from the 'Telstra Technical Department'. I allowed him some time to explain how my home computer was vulnerable to error and hacking. He then got me to open 'teamviewer.com', and he was going provide a
verification number', so that he could then view and access my computer remotely. When I told him I was not proceeding and wanted a proposal from Telstra, he got anxious, tried to hang on to the call and even called me 'childish'. I hung up!

Scam caller.