I am new user of Ubuntu. I am using Ubuntu 12.04 LTS. Almost everything is working fine, but I can't access the internet. I am connected to my mobile broadband. It is ZTE MF691 USB modem. When i connect it, it says connection established.
Does it show connected in the status bar as well? Sometimes, mobile broadband shows connection established but takes a little time to start working.
Try ifconfig and ping in a command line to check if things are working fine. A little hint in this thread Enable mobile broadband not working
I hope your data package is not expired ;-)