If you haven't changed any of your regional settings (ie from Canada to U.S.) your Cortana will be the Canadian version which is in Alpha. Users can get the U.S. beta version if they change their devices region, language and keyboard settings all to U.S.
The Denim firmware update should have come pre installed on your phone. It came with Cortana and the live folder functions amongst other things. One of those updates was a passive listening setting for Cortana. So basically you could say out loud "hey Cortana" and give her commands without even touching your device.
The thing is that it is said that only phones with a certain processor can handle that function, which I don't think the Lumia 830 has. BUT it does have the Sensor Core required for the "Hey Cortana" feature to work.
But if you are being interrupted by Cortana while you are speaking it may be because of that "Hey Cortana" feature. It may be detecting your voice/keywords and responding passively without you even engaging the phone.
If you disable your location setting and wifi/data connections Cortana will not work until those settings are re-enabled. I only turn that function on when I use Cortana as having that setting enabled all the time really eats away at my battery life.
Here is a article I found relating to the "Hey Cortana" function if you want to know more.