got a dlink dwm-156. vendor 2001 product 7d01.
They have i386 and amd64 debs. The deb has udev rules, usb_modeswitch
renamed to 3g_modem_switch, a script to modprobe usbserial with the vid pid
and ppp scripts stuffed into /etc/3g_modem_connection and /etc/ppp.
The udev rules file has some lines to autoconnect, using modem-manager, so
comment those lines if you dont want to auto connect and rake up bills.
Essentially one does not require usb_modeswitch. merely ejecting /dev/sr ?
and modprobing usbserial with the vendor product that shows up AFTER
ejecting /dev/sr ? does the job.
With the help of the udev scripts the whole thing is automatic.