Using Voice regonition with Android Lollipop 5.0.2 with Bluetooth Headset, how can I do this?

[AC Question]

Using Voice regonition with Android Lollipop 5.0.2 with Bluetooth Headset

I would like to use my Bluetooth headset with my Android Lollipop phone (Vodafone Smart Ultra 6 - stock android) using voice recognition so I can call someone in the car without having to physically touch the phone

Once the Bluetooth headset (with voice recognition) has been paired with the phone - when I press the button on the headset to activate the voice recognition so I can say who I want to call nothing happens.

How can I activate voice recognition on the mobile or is there an app I need download?

Thanks