If you cant unlock your screen and it seems unresponsive, I would reset the phone.
Press and hold the Sleep/Wake button and the Home button together for at least ten seconds, until the Apple logo appears.
From: iPhone, iPad, iPod touch: Turning off and on (restarting) and resetting
You can also disable Siri if you wish:
Settings > General > Siri.
From: iOS: About Siri
All the best,