Bingo!
This is the correct answer. If your website has a great deal of information, graphics, videos, music... it can very quickly run through your allowed bandwidth with few visitors.
On the other hand, if your website has just a single page that's 1K long... do the math.
But it sounds like you're talking about free website hosting... Real hosting is so cheap today, just buy a good package.
Or if you want to play around, there are many sites that as far as I know have no bandwidth restrictions (such as Wordpress.com, Blogger, Hubpages, and similar)