Caller: Scammers for all I know

They've just called me, they knew my name. They said they were from Telstra and that my internet IP somehow went from private to public. They insisted I had to follow their instructions to fix it or I could lose everything (?!)
I told them it sounded like a scam and there was no way that number was from Telstra. I basically said I needed an official communication from Telstra or I could not believe them. They hung up and when I tried to call them back...surprise! The number was diaconnected! Do not trust anyone calling from a general number rushing you into doing things and trying to scare you! Don't do anything.