I have a few stunts I do when they call.
1) Say my parents are on holidays, and when they ask when are they coming back, I say oh in 7 months. They're in Swaziland.
2) Burst in to tears, and insult them and ask why would they call at a time like this? My parents are dead, how could you even mention their name?
3) Take the phone to the TV, put it on Disney channel and make them listen to whatever show is on.
4) Pretend I'm the adult, and ask them to read out the terms and conditions of the product. I ask them lots of questions about the product, and then say thank you for your time and hang up :)