irrelevant, Completely agree.  I never accept calls like this unless I've done something like just used my credit card.  Even then I still ask where and what amount.

I guess though if criminals were smart they could pay a corrupt shop-assistant to text them your mobile number, credit-card number and code as soon as you had made a purchase and then call you claiming to be from the card security section of your bank.

Then  they could ask you to confirm all sorts of stuff.

You CANNOT be TOO careful nowadays.  It is a pain.  The only solution is capital punishment for fraudsters.