whilst it might have a sim card slot, it might not have the 4G modem installed that uses it, but as the slot has to be accessible from the outside it'll be included on all machines regardless of whether the modem is there or not.
Are you sue the SIM is a valid one and has credit to make a call? Can you test it in another device or phone? There doesn't seem to be a specific driver for the slot in their website or its link to DriverGuide.
whilst it might have a sim card slot, it might not have the 4G modem installed that uses it, but as the slot has to be accessible from the outside it'll be included on all machines regardless of whether the modem is there or not.