When other hosting companies says that they are providing you with “unlimited bandwidth”, what “unlimited” means is that they think you won’t go over a certain amount of bandwidth, so the limit that they set will be more than enough for you. If you read their Terms and Conditions carefully, we’re sure you’ll find that their “unlimited bandwidth” is really limited to only a certain amount.
It is NOT possible for any Web Host to provide you with unlimited bandwidth. The hard-drive on your Hosts’ web server has a finite amount of disk space. There is no such thing as “unlimited”.