Question about blackberry + data plan consumption

[hexxeh]

hello.
I recently got a Blackberry Bold 9000 with a Dataplan on Cosmote-Greece carrier, that gives me 100Mb data usage. When i noticed that when i m
connected on a trusted wifi network, my device uses Wifi for Browsing and network traffic, through my Private wifi network -internet connection at home.
When this happens, the data transferd, are counted as data of my current dataplan, ? if i use a wifi connection to download a video , will it use my "100mb of dataplan" to get downloaded?

ty in advance