In my experience they're security calls. UK has good opt out marketing rules for legit companies.

But the usual security call is exactly like a spam call, no authentication from their end, immediately requesting id verification "answer these security questions", and refusing to go off script.

People have been asking for years to be able to lodge a security challenge code on their profile that can add confidence in the caller. Given there are already multiple security questions on an account, this could be a process change: the security challenge script becomes "the first and sixteenth characters of your mother's maiden name are 7 and F, what are the third and fifth characters of your first pets name".

Yeah as sibling points out, lots of orgs have scammy official security calls. This leads to a dance I have been through quite often.

   <phone rings, I pick up> Hello
   Them: Am I speaking to Sean Hunter
   Me: Yes
   Them: This is <rubbish bank who should know better>. Can you confirm your <date of birth/full address with postcode>
   Me: Yes
   Them: Err, … sorry I didn’t quite catch that.
   Me: Yes.
   Them: <thoroughly confused>I asked whether you can confirm your <date of birth/full address with postcode>
   Me: Yes.  I can.
   Them: err… I can’t talk to you without you passing security.
   Me: You called me.
   Them:  I’m sorry…?
   Me: You called me.  You wanting to talk to me about something is your problem.
   Them: I need you to pass security before I can talk to you.
   Me: OK, well.  Have a nice day.  <hang up>

Almost this exact thing has happened multiple times with one of my bank accounts which I can’t completely shut because of boring reasons but I have basically deprecated because they do this sort of nonsense. My main bank now is much better.