Going through the email "opt out" process will do nothing more than having your email, name and phone number being sold to a number of third party scammers which will result in even more invasions into your privacy.
     The best thing I have found is to just keep saying "hello" a few times, especially talking over the heavy middle eastern accent on the other end, and then hang up.   They usually think they or you have a bad phone (yes, they quickly figure out it is not a problem at their end) and you will be removed as a good contact.