It's not the bandwidth that's the problem.. That's just how fast your transfer speed is.
You are just transferring a ton of data.. ;)
My office uses MiFi's for the staff that goes out of the office to keep in touch with the office and such..
Well, one MiFi used up it's 5GB monthly limit in 3 days! I called the staff person and finally got them to admit they were using it to Skype with..
The only way I know to track your computers data use is to check the Network Connections properties and look at the "Activity" readings.. XP boxes uses "packets" and who the heck knows what that is, but I'm sure there is some sort of conversion you can find on it... Windows 7 uses "bytes", which you can also convert to MB or GB, but that's the only way I know, other than your service provider that obviously tracks it to to the MB..
Good luck!
Mitch