I have a D-Link DWM-156 HSPA modem, that I bought just a few days ago. The modem has drivers in its internal storage. There are Debian packages (.deb) for both i386 and amd64, so obviously I installed the amd64.deb using Software Center:
3g_modem_connect_D300_amd64.deb. Then I did:
sudo modprobe usbserial vendor=0x2001 product=0x7d01
I have confirmed that the device switched to usbserial mode from usb-storage mode, as the product ID was a706 before. Although there are no commands like
usbdeviceswitchdlink after installation.
But here is the thing, the device is detected and I get the mobile broadband options in the network menu only when a SIM card is not present in the modem. If a SIM card is present, the modem switches to usbserial mode but after that, there is no change in the network menu. I can't use my modem in Ubuntu at all.