I have an iPhone.can't download apps?

I just got the 3G. It's unlocked and I can't download any apps! It'll either say "this app is not compatible with this iPhone" or it'll say something about the iOS version and how I need to update it. But I don't have any ios updates in my general section? What do I do? Shuld I take it to an apple store tmrw?

Plug in computer and restore and try again. If that' doesn't work bring it into your local Genius Bar

Well that's the story with the 2G & 3G I'm afraid. Most apps require iOS 4.3 & neither can update to that. You'd have to get an iPhone 3GS at least.