Re: USB modem detecting as Mass storage
In Network Manager, go to Edit Connections,then the Mobile Broadband tab, then click Add.
If this doesn't work, then your Ubuntu is probably too old to support your device. Try a later version like 12.04 or 12.10.
I try to treat the cause, not the symptom. I avoid the terminal in instructions, unless it's easier or necessary. My instructions will work within the Ubuntu system, instead of breaking or subverting it. Those are the three guarantees to the helpee.