3G nightmare!!!

Not a dream. It was real!
My latest Starhub phone bill was 3 times my normal monthly bill!!!
When I first saw the bill, I thought it was the internet (my galelry one) bill from Singnet.
But it was from Starhub. Was it inclusive of the Maxonline?
No leh! I had stopped the subscription to the slow Maxonline for more than 2 years.
I looked further down the bill, searching for the culprit which jacked up my bill so much.
Wowliao!!! It was the Gee! Data Usage - 11mb and 227 kb, which cost me $114.91!!!
I was shocked.
Since when did I use so much on the upload and download through 3G?!
Checking through the log on my phone, the total data sent and received was only 2.2mb, which I was unaware too. My conclusion was that perhaps my wireless internet connection was lost and it switched to using 3G to download and upload. Even though, it shouldn't be that much. Or was it the billing errors on the Starhub side? Someone tapped into my 3G line? (which was very unlikely) The only way is to ask Starhub to print out a detail billing for me. From there, I should be able to know the reason. I will need to find out from them how to avoid switching to using 3G to download and upload data. I have try setting on my P990i, but don't know whether I did it correctly. My initial intention of getting this phone is to use the wireless internet connection through the network at home , my gallery and free wireless@sg (also in Mcdonald's), not using 3G (except for video calls). Heart pain..........
Must do some setting for my wife's N80 when she gets it this Thursday too.