The reason you are seeing that problem is because you need to download the USB modeswitch package as well as the VMC package you already have.
You can download all the relevant files from the Vodafone betavine site:
You can install the .deb packages by using
After running both of those commands you may have broken dependencies. To fix them (sudo or run as root):
dpkg -i usb-modeswitch_0.9.4-1_i386.deb
dpkg -i vodafone-mobile-connect_1.99.17-8_all.deb
That should get the USB version running for you.