The voices are mostly very distinct and varied, especially the Game Wizard's delivery. Though I can see how some reviewers think the person calling for assistance has a more whisper/raspy quality to his voice. It does aid in differentiating his voice, that's for sure, but it didn't seem like the best voice type to implement.
The writing is also good, too. The conversation between the tech support and the individual is fluid and often times hysterical, though a part of me wished that you incorporated him saying that it's his first time calling for tech support in the beginning. Otherwise, not a lot of people might be able to distinguish this for suiting the theme of this contest.
Lastly, the mixing was pleasant. It didn't go overboard, and some of the instances where you applied it, especially when he interrupts the Game Wizard by pressing 1, was perfect. Good job on also applying the music in the background and not having it at a level where it's distracting. It's the best volume, and it really does suit the situation.
Overall, nice work. I think you do stand a good chance overall in the competition.