Relatively new service i have seen a number of Trading Standard Departments recommending.
" Do you get annoyed when you fill in a form and have to enter your phone number even when you know that the company doesn’t really need it?
What are they going to do with it? Who will they give it to?
Your privacy is valuable – protect your phone number with trueCall38!
The solution: enter our phone number 0333 88 88 88 88 (that’s three threes, eight eights) as your phone number, and if, or rather when, they call, those cold call culprits will hear our short but sweet recorded message:-
"trueCall38 is handling my calls. I prefer not to be contacted
by phone, so please contact me via my email address.
Goodbye!" "
http://www.truecall38.co.uk/