It's ok- we have just established that the computer is sensing the modem as Mass Storage instead of as a Modem, though. So now we know what to fix.
You may need modeswtich:
sudo apt-get install usb-modeswitch
This is because you need to change the mode for the USB device (modem) to modem instead of storage.
Use (replace _____ with your modem name):
lsusb | grep ______
Note the Vendor ID and the Product I.D.
Making a fictitious I.D. up: 12d4
Replace the fictitious I.D. with the actual one you noted above:
grep 12d4 /lib/udev/rules.d/40-usb_modeswitch.rules ATTRS{idVendor}=="12d4", ATTR{bInterfaceNumber}=="00", ATTR{bInterfaceClass}=="08", RUN+="usb_modeswitch '%b/%k'
Extract the config:
tar xf /usr/share/usb_modeswitch/configPack.tar.gz 12d4(Replace this with your actual ID):4d21(replace this with the Product I.D. you noted above)
Use modeswitch
usb_modeswitch -v 12d4(Replace this with your actual ID) -p 4d21(replace this with the Product I.D. you noted above) -c 12d4(Replace this with your actual ID):4d21(replace this with the Product I.D. you noted above)