Googlebot visit my webpages daily but no bandwidth increase. Is this mean Google can't read my webpages?
use google sitemaps www.google.com/webmasters/sitemaps/ that will help get your pages crawled and tell you about any potential errors
And whatever you do, do not have the spider crawl faster. It won't matter because you want the bot to creep along your pages and suck up all the content available.
you can see that and more details at your sitemap page. prepare a sitemap and verify your page . you will all these detail on sitemap page
What stats do you use? Some don't show bots as real traffic and count it differently. If you build up links to your site it will get you indexed. you will need at least one good link to get indexed in google.
How can this happen? Google visit your webpages, and then definitely it bites some of your bandwidth. Or you just means no sigificant increase?