The D620/630 series had an option where you can purchase an internal mobile broadband data card. Like the iPad has a "Cellular" version where you can insert a sim and use data, the D620 has the same capability if you have this card. Please note, the Dell card is Carrier Specific (AT&T, T-Mobile, Sprint, Verizon have their own and are not interchangeable).

Here's a video on what it looks like in the laptop.

https://www.youtube.com/watch?v=6yaZXxNy...

Ebay sells this:

http://www.ebay.com/itm/DELL-Latitude-D4...