I’ve read with interest some of the messages relating to scammers. Having once had a role where my company needed to educate hundreds of employees on how not to get scammed, I’d like to make a few suggestions:
Do not tell the scammer “there is no such company as BT Openreach, they became separate companies in 2017” This is just giving them information they can use in the future. If scammers keep telling people they are “BT Openreach” they are confirming they are not legitimate.
Don’t get mad with them. It will only raise your blood pressure.
Don’t blow whistles, sound claxons or make other loud noises.
Ideally, don’t engage with them at all. Just hang up.
If you want to retaliate and are not concerned about your phone being engaged for a while, ask them to hold on for a moment, then place your phone on your desk/table etc and go about your business. After 15 minutes or so, pick the phone up and see if they are still there. If they are, excuse yourself again and repeat until they give up.
All the time the scammer is holding on, waiting for you, is time they are not using to scam someone else.
If you think it might be a genuine call, there is nothing wrong with you asking them security questions. A genuine caller will be able to answer questions about you and your account that scammers cannot. You can also test a caller by deliberately giving a wrong answer to a security question. If they accept the incorrect answer then you know they are scammers.