Ask them their name/ last initial, employee ID or unique identifier for the conversation, direct phone number, job title and what location they're based at. Scammers will pretty much always refuse/argue/hang up on this (once I had one start insulting my mother in Hindi when I asked him this). Then call your bank's proper number and verify all of these details.
(But in any case your bank will never call outwards to you, unless you've specifically requested that, which you almost never do.)
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Unfortunately my UK banks (and others) DO regularly make calls to me unannounced and demand my ID to 'prove who I am'. They are not scam calls and the callers cannot understand what they are doing wrong. If I'd had more strength in the last round of this stupidity I'd have done a number on them with the regulator. (I used to work in finance and was the director of a regulated financial entity, so I think I'd have a head start.)
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