On March 1st and 2nd I had 60k+ page views, 60k+ hits (webalizer stats) for a total of over 7GB of bandwidth use, the rest of the days until march 9 I had, which I think is the normal use, an average of 40MB per day, this almost eats the whole month's enchilada, I was wondering what could be happening?
Something similar happened to me a while back,someone hacked into my site via my wordpress and was able to add files to my root folder,including a video,maybe worth checking.
If you need more bandwidth for a month, please ask for it.
About the issue, it could be that a website is linking/using an image (or several) of your website. Or a page on your website got popular on some social media website like Reddit or Digg. You can probably find the cause in your logs. (referrers and visited pages)