Stuart Edge is somewhat starting to become a legend lol .. I'm guessing it was all staged. He asked someone they know for the persons number, I'm assuming he told them that he was going to play a trick on them.
He then saves the number as "the cute girl next to me"
If you want to use Siri to do the trick, you'll need an iPhone dude, or any other apple product that has Siri and makes outbound calls.