It's not an excuse Halk, not least because Banks make zero attempt at all to prove who THEY are.
ANYONE can call you and ask all these questions saying "sorry, we have to be sure", there is no recourse for someone doing this to you, pretending to be the bank and then stealing your money, the bank will blame you when the bank has NOTHING in place to make it easy to prove its your bank calling.
M&S CC card I have, the constantly cancel payments for fraud reasons, phone up and ask if I made it, but it could be anyone.
Its really simple, bank calls you, asks you to call number on the card, on their website, whatever a known for instance HSBC number, and they give you an extension to call back on, for free no matter where you call from. It's that simple, they tell you they want to talk, you phone a known HSBC number and get straight back through to the same person, no confusion.
This is the thing that irks me, M&S ask questions that I can't possibly remember(i'm not the main account holder for one thing), but refuse to make any effort to prove who they are AND they will screw you for giving your details out to anyone else, its insane, completely insane.
How many people are giving away their details to the wrong people because someone phones and randomly asks for details to prove themselves, its probably a huge source of bank fraud and the banks do smeg all to fight it, meanwhile making your life more difficult.
Hell, a second pin number for your account where YOU can ask them for any three digits, or a password, or both and if the bank can't supply it, don't talk to them.