I haven't answered a nuisance call for at least 18 months and I have a normal BT landline. The nuisance calls still come but they do not get through to me. This is how I do it.
First of all the people in my contacts have a distinctive ring tone so I know immediately if it's a friendly call.
All the rest go through to the welcome message on my answerphone which simply says "if you are selling, after money or seeking personal information please hang up now or leave a message after the tone and I will get back to you".
It is surprising how many end the call immediately it detects an answer phone, presumably these are the silent calls and automatically terminate. Some listen to the first few words and then hang up, presumably looking for easier prey. A very few actually leave a message which I delete!
Just for fun if they leave a number in my call list I Google it and it often shows other people who have answered it and tell me what I have missed. You soon get used to the regular callers.
I am registered with the TPS but that is a voluntary scheme which firms who want to contact real leads will use to save their time. Time is money after all. It does not apply to those who choose to ignore it and use software to make thousands of calls daily.
In the old days when I did answer these calls I would invariably say they had got the name wrong. I would tell them my first name is Isaac and my second name is Hunt, then ask them to repeat it. Sorry could you repeat that again.
Then the penny usually drops and the phone goes dead.