Im assuming thet the odem shows up in system/resource/usb...
The device does not show up as a usb device in system ports (serial devices) ?
If it does, then set the baud rate to 9600 (sprints use this rate for the cmd channel)
Look under ppp/interface if it shows then set it up as in the example in the mikrotik wiki..
If it does not show under system/ports, it has probably not been "defined" yet..
Send a sup-out to "
support@mikrotik.com " desrcibing the issue and make sure the device is plugged in when creating the sup-out..
They may ask you for remote access to the device to look at the device structure.. let them....
The have done it for me and with great outcomes..
Hope this helped..