Spoke to someone at (03) 9962 0676. Apparently calling from the Telstra technical department. Did not even attempt to verify my details, or himself. Said my IP address has been compromised and asked if I had made any recent changes on my account. I played along for a few minutes saying, "Oh no that's horrible", then I said, "I'm not with Telstra." He said it doesn't matter and that there are different areas and that it's about the service and doesn't matter if I'm not with Telstra.
When I had had enough, I said "Well I have no way of verifying you, so have a good day". He said, "Well fine we'll cancel your service f**k off" and hung up.

Suspected scam. My mobile blocked asap. Thank you Samsung.