Cold call on my home number, terrible accent - but knew my full name, address etc (and I'm not on the electoral roll) - claimed it was about a reward voucher scheme for prompt credit card payment (ok, so no way am I giving out personal information to these people - and card companies *want* you to pay late).
Endless waffle about the benefits, basically hotel vouchers, but willing to go off-script and answer questions - well, apart from "Why don't you just post the stuff to me then, rather than give me all this waffle?"
Anyway - eventually we get round to the =A399 administrative charge, and I say ta-ra.
Seems to be a relatively new one, though police aware in other areas:
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the caller had better spoken English, I could imagine someone might in a distracted moment not realise the call isn't from their credit card company.