Just got a call from "telstra technical dept" stating my...

Just got a call from "telstra technical dept" stating my internet speed was very slow. I requested the tel no for the dept, he started saying in an Indian accent 1800, then stopped, so I asked for the rest of it. He told me to F off !!! I know its a scam, have had so many calls from various numbers either to do with the internet, mastercard, visa card etc. First time one of them has resorted to such language. I am on the do not call register.