M2 HSPA+ card not detected properly

[lapo]

Hi,
My first post here - so please be gentile.
I have a Qotom Q555G6 - it has 6 LAN ports and 2 mini pci express ports.
I added in one of the mPCIx ports a Sierra Wireless 4G modem (MC7305) but it isn't seen by the OS as cuaU device but rather as a ugen0.3 device - as far as I understand, as a USB device.
I cannot set it up as a PTP device, it doesn't show in the list.
If I issue a "cu -l /dev/ugen0.3" I get back an "Unsupported speed 9600".
Any tips for how to get the connection going for such a device?