Nokia Lumia :: 900 Data Counter And People Tile?

Is there a data counter on the Lumia 900 that I can't find? I've tried to call the 3282 data number, and it always tells me I'm at 0 even though I know i've been on the data network and not wifi.Also, can someone explain to me how much data something like the people tile/email account setup uses? I've never understood apps like that coming from suuper old phones. Is it constantly checking your email/facebook? On some time interval? I'd really like to set up facebook and such with the people tile because it seems really nifty, but I don't want to go over my 2gb plan. I just don't terribly understand how it all works, and i'd be willing to try it out if I could see how much data i'm using..but that goes back to my first question...In the past when checking email/facebook I'd always just use the internet browser on my old Nokia e71x, and it wasn't giving me updates in real time like I know this guy is capable of. I'd like to use it, I just don't wanna eat up my data plan.