I've had one of these so far, but I just treated them as I did when they rang saying they were Microsoft and that they had had a report that my computer was infected.
I just said that my computer wasn't on, though it was running slowly now they mention it, and if they waited I'd switch it on and let them help me with it as I had some banking stuff to do.
Then it's just a matter of getting on with whatever you're doing, make a cup of tea, mow the lawn, and so often they are still there when you come back, when of course you just hang up.
Invariably they ring back as they are now convinced they have a sucker and you just repeat the whole process as you switched off the computer when you were cut off etc etc.
It might be childish but it keeps me amused for half an hour. Its so sad when you have to rely on scam phone call for much craved human contact.