Just to clarify, you are talking about a SIM card slot and not a SD card slot, right? In general, I would recommend you to check the laptop’s manual for some more information about this. The truth is that the full hardware required for a SIM card usage is optional and you may need to have a Mobile Broadband mini-card connected in order to use the SIM card.
If you already have it, then open Device Manager and check if there is a driver compatibility issue. Check the card manufacturer’s web page for some more details about driver installation/updates.