Suspect it was 'you have an internet problem' type call as I've had a few over the last few days. I think that this was yet another. I told them that I don't have any problems and said that they're scammers and crooks and to get lost. They keep changing their numbers, too, which I wish that Telstra would do something about - the number prefixes are all Telstra's from what I can tell (0419).