Caller: Scammers

Another scam phone call from some Indian person telling me he was calling from Telstra about my faulty internet connection, I have been getting so many of these calls lately, I've just had another one from a number that came up as a NZ number, I am sick of these fraudsters calling, how do they get the phone numbers?
I hate to admit it, but now when they call & I realise they are just scamming grubs, I abuse the crap out of them, I hope Karma gets them!!