If the new Touch N Go can't understand, it throws up a menu on the screen of available commands. If, when you do "call by name", the system finds multiple matches, (e.g. more than one John Smith; or mobile & landline) the system will display a list on screen and ask which one you want.
Definitely clean the throttle body next, mine had a similar problem with low revs stalling at junctions etc. Gave the throttle body a really good clean and all was well again. Phil
On the topic of voice commands, the other day, I had cause to give a blast on the horn and call another motorist an idiot... to which, a second or two later, the car said "Pardon?" - perfect timing, and hilarious. (when I went for the horn, I accidently hit the voice input button!) :)