3gs gps

GPS experts,

My factory unlocked 3gs iPhone has a pay-as-you-go t-mobile sim. The phone works well as do (most of) the apps I've loaded. My problem is with the GPS function.

I think that Maps should perform some sort of GPS tasks (even outside of a wi-fi zone) even though my particular low-level t-mobile service does not include data service. Is this true? I did download 2 separate GPS apps (Skobbler GPS Nav2 and Waze) which sometimes work, but never well.

What settings should be made in order to get the "built-in" (via Maps) GPS-E to operate? I don't particularly expect it to have voice commands but it seems that it should locate me even when I'm not in a wi-fi zone (in other words while I'm driving). Of course I have <Location services> on. In <Network> what are the proper settings for <Enable 3G> and <Cellular Data>? Remember, I have no Data service through my carrier but I thought that the GPS-e worked by sensing the location of cell towers not by accessing "data."

To sum up--does an iPhone 3gs have a GPS function? How to enable it?

Thanks, JimH