I have had 5 calls today from a withheld number. I reported the calls to TT after the fourth - they confirmed that it is a scam. Next tine he called I told him. He hung up immediately. I had read that the caller probes, wanting the answer 'yes', but maybe that's a myth. He kept saying 'can you hear me' and 'are you married?' Has anyone else had these calls?
I had them a lot when I was with Talk Talk, I just told them to send me an email and that ended the conversation. I still got regular calls and did what I've found to very effective with unsolicited sales calls and just ignored the phone without switching it off. This soon gets you off their list as they can't call anyone else until you hang up.
Try it, I've had great success that way