For those of you who don’t believe that this works or don’t care to try it for yourself, here’s a video of an iPad 3G Micro SIM card being used in my stock iPhone 3G running iPhone OS 3.1.3.
You can of course try this yourself by following the instructions outlined in my previous post.
Will this work on an iPhone 3GS?
Yes, and also the iPhone 2G.
can you make phone calls with it?
Yes. Using VoIP.
I posted instructions for Google Voice users here: http://hijinksinc.com/2010/05/24/free-sip-calling-with-google-voice-sans-gizmo5/ but you could also use Skype.