jj
I am in your situation right now but with only the minimum amount of data.
I had 3 data overages for a total of $45 added to my bill. i called CS and the rep advised me to upgrade my data plan. i guess she didnt know that she couldn't spend my money for me. as for help or a credit, she ignored me but i am actually going to call CS again shortly. now one strange thing about my samsung captivate is that the battery was dead right after i got the message. i turned off the phone, charged the battery overnight and the next morning upon power up, i got another data overage text and my battery was again very low. The last thing i did was to charge the battery again and then pull it from the phone for at least 7hrs. idk the reset time but my phone did reset (cold boot) and the issue was gone. how i got the problem , idk but att hasn't been helpful as of two months later. i've searched online and a few things come up but Att doesnt kow why this is happening. I would suggest that you pull your battery for a few and see if the issue still exist. i will keep you updated on my call to CS tonight... also the rep suggested i visit a retail location but they are they there to sell you service not diagnos the unknown.

hope this helps

d