My mum has moderate Alzheimer's and one of our concerns was her gullibility over the phone. She trusts everyone and had signed up for a couple of scam telephone preference callers and unwanted insurance - we found out when we used our LPA to help her with banking.
I did a lot of research into call blockers and found out that most of them require the person answering the phone to make decisions whether to accept the caller and press certain buttons. Not something mum can do! But I found one called True Call Secure which is perfect for people with dementia. Now, only numbers from a trusted list which I have set up go straight through. All others hear a recorded message that I made, saying that their call is blocked and if they want to call mum ( I used her name so people know they have the right number) they must speak to me on my mobile first. This means I have to answer all calls on my mobile even when I don't know who it is but in the seven months since we installed the blocker, no one has needed to call me. As part of the initial price, I get a years free access to a website so I can monitor the calls, both made by mum and received, and input new trusted numbers as necessary.
We have hidden the blocker under a table so mum cannot mess with it! Mum tends to dial 1471 and then call everyone back which makes her rather vulnerable. To protect her from giving out her bank details over the phone, I also scratched off the security number from the back of her card!