It's a tragedy that some folk are caught by the Scam.
I said to one chap who announced himself with a uk sounding name, "Is that your real Christian name" and he shouted back at me " I'm not a Christian" and duly cut-off the call.
to get rid of the problem once and for all have a look at the BT 8500 - it only lets through the calls in your address book and gives you the chance to block these sort of calls very easily.
You have clearly learnt from yesterdays experience when you told people 'gently' and today you took the bull by the horns and told this guy 'brusquely'!
Well, ordinarily I might have been tempted to tag this twit along, and have some fun with him, but I was just about to do my morning ablutions, so decided short and sharp was the order of the day !
A few weeks ago, I had some entertaining fun with a similar Asian-sounding chap, by speaking Welsh to him, mixed with a tiny bit of English. After a few minutes, he gave up !