I've just joined the Community, so sorry if someone has come up with this idea before - I haven't had time to read all the posts!
Having been bothered by scammers claiming be ringing from TalkTalk I have a suggestion as to how TalkTalk could stop this. Would it be possible for all customers to be given the (optional) choice to have a “telephone contact password”.
This would work by the customer giving TalkTalk a password which they (TalkTalk) would use when telephoning the customer. This password could be kept on the Customer’s record on the TalkTalk computer system. In that way, for example, if I received a call from someone claiming to be from TalkTalk, I could ask them to give me the “telephone contact password”. Only someone genuinely calling from TalkTalk would know this.
It may be that this may be difficult to do from the point of view of altering customer records, but I thought it was worthwhile suggesting it.