I have installed ubuntu 13.10, and have difficulty in mobile boradband. I have a Tata Photon usb stick, configured as Huawei EC 1260. It shows up in lsusb as 12d1:140b, but does not show up as device when I try to add a mobile broadband connection. It also does not appear in network manager icon.
Your dongle is supposed to switch into modem mode automatically but it doesn't. The problem is similar to mine: Huawei e173s 3G USB dongle won't switch into modem mode - except that the device is different, and so may be the exact cause.
The program which does auto-switching is usb_modeswitch. The first thing you should do is to enable usb_modeswitch logging: http://www.draisberghof.de/usb_modeswitch/#trouble (that section also suggests some common problems/solutions).
After looking at the log file, you will be able to localize the problem and cross-check with forum threads such as this: http://www.draisberghof.de/usb_modeswitch/bb/viewtopic.php?t=681
Unfortunately, I can't give you an exact answer to the problem as causes may vary depending on device type / firmware version / kernel version; but above should constitute a reasonable troubleshooting guide. You can follow the steps and write back.