Did you order an internal WWAN card?  Or is this an external card?  What model card?  What model system?

I've bought laptop in local store, so it was pre-configured and I've ordered no hardware. As far as I remember there was WWAN card in specs. Laptop model is Dell Studio 1558 (210-30963-Blue). Is there a way to check WWAN card existance? And also, I thought that SIM-card slot under battery tells me that card is installed, isn't it?

A SIM card slot means nothing without the WWAN card. Download a manual and verify the existence of the card. Given that a WWAN card costs an extra $125, I rather doubt that your laptop has it.

I've bought laptop in local store, so it was pre-configured and I've ordered no hardware. As far as I remember there was WWAN card in specs. Laptop model is Dell Studio 1558 (210-30963-Blue). Is there a way to check WWAN card existance? And also, I thought that SIM-card slot under battery tells me that card is installed, isn't it?

So, SIM card slot can be just a slot without any hardware connected to it? Can you tell me where I can download this manual?

The SIM socket is there whether or not you purchased a WWAN card.  It is connected to the system board.  The manuals are here:

http://support.dell.com/support/edocs/systems/studio1558/en/index.htm

ok, thanks, seems like there is no wwan card installed. thanks for your help.

The SIM socket is there whether or not you purchased a WWAN card.  It is connected to the system board.  The manuals are here: http://support.dell.com/support/edocs/systems/studio1558/en/index.htm