I do a similar thing, I assume the calls are coming from abroad so try to keep them talking as long as possible.
Then ask where microsoft is on my mac ?
or how do I do that with Linux ?
They usually just hang up straight away, you are lucky to get an apology.
I can remember the first time I had such a call being quite worried but this is old hat now
If someone has a similar way of getting rid of PPI callers or double glazing/home improvement salesmen please let me know
Kind regards
Tony Cross