Black Wi-Fi Problem?

[Immerse]

Iv been trying to get my head around this put no matter what i search my results come up blank or supporting the fact it can be done....

For some reason in Wi-Fi battles i can only use 3 out of my 6 pokemon in single matches no matter what options i take and it's the same in union room. It's really frustrating because i can't use my whole team so i can't use tactic's i would usually use so it becomes a game of luck and power. I know it's possible to have 6v6's because there is an abundant amount of vid's on youtube; http://www.youtube.com/watch?v=K9T-04NyPYk&feature=related one example.

I was hoping someone knew what it was that i was missing or something...

Thank you in advance :3