Great phone prank
We all by now know how annoying those calls that try to sell you something.
But you can have some fun with them to. Have a look at this little video and maybe it gives you some idea’s 
Let me tell you what I like to do. When I get called by a telemarketing company I put there nr in my phone so next time they call I know it is THEM. And then I just like to pickup and say “I AM NOT INTERESTED IN YOU S..T” and that normally keeps them kinda surprised (to say the least).
I would say invent something like it your self and share it with us maybe if we all do something like it we will have FUN with them instead of getting annoyed