The key-thing is:
$ sudo rmmod usbserial && sudo modprobe usbserial vendor=0xc88 product=0x17da
(apart from the authentication "
The modem configuration is trivial, and can be done either by editing ppp scripts or using the desktop GUI, doesn't matter.
Frankly, I couldn't see any benefit or hacker options in ppp config.
What keeps bothering me is the fact that I have to eject the card, reload the module and insert the card again each time the connection falls or the machine reboots.
(obviously I have modified my /etc/modules with the proper vendor/product, but it doesn't seem to work as expected)