Don't even start talking first. They can clone your voice just by you saying "hello". Let them talk first.

Or don't pick up the phone at all unless it's from one of your contacts.

It's a scam, they'll attempt to phish account credentials. Googling for [scam call "interest in the financial market"] turns up scattered reports.

Maybe I am missing something but that doesn't seem super strange. Rather typical of trivial nuisance. Are you thinking the call may be "AI" driven?

Several comments in this recent thread [0] suggest the same advice I now give as standard [1], that if you pick-up at all from an unknown number do not speak. Give a few seconds of silence and let the initiator speak first. We need more common advice on handling unknown calls [2]. FWIW the ISSG of British Computer Society are holding a conference on communications supply chains and telecoms source validity this spring.

[0] https://news.ycombinator.com/item?id=39304736

[1] https://cybershow.uk/blog/posts/scamicry/

[2] https://www.ncsc.gov.uk/guidance/phishing